我项目用的vue-element-admin的模板，里面有导出的示例。不过只有一级和二级，

本项目只展现，导出三级表头示例，

可以参照我添加三级表头方式，进行，添加4,5,6等多级表头导出。

如下示例，先布局好，此处参照项目的示例即可，

methods: {
    handleDownloadExcel() {
      // this.downloadLoading = true
      import("@/vendor/Export2Excel").then(excel => {
        const multiHeader = [
          [
            "序号",
            "旅行社",
            "国内（温台意外）",
            "",
            "",
            "",
            "",
            "",
            "",
            "境外（含港澳台）",
            "",
            "",
            "",
            "",
            "",
            ""
          ]
        ];
        const multiHeader2 = [
          [
            "",
            "",
            "门票消费金额",
            "A类(张)",
            "",
            "B类(张)",
            "",
            "C类(张)",
            "",
            "门票消费金额",
            "D类(张)",
            "",
            "E类(张)",
            "",
            "F类(张)",
            ""
          ]
        ];
        const tHeader = [
          "",
          "",
          "",
          "全票",
          "半价",
          "全票",
          "半价",
          "全票",
          "半价",
          "",
          "全票",
          "半价",
          "全票",
          "半价",
          "全票",
          "半价"
        ];
// this.headVal是一个数组，  表头所对应的字段，这里未填写，
//比如：['id','age','name'],随便写的，以你的实际数据为准。
        const filterVal = this.headVal;
        let list = [];
        if (this.tableDataExcelType == 0) {
          list = this.tableDataExcel;
        } else {
          list = this.tableDataExcelAll;
        }
        const data = this.formatJson(filterVal, list);
//进行所有表头的单元格合并，建议一行一行来，不然容易整乱
        const merges = [
          "A1:A3",
          "B1:B3",
          "C1:I1",
          "J1:P1",
          "C2:C3",
          "D2:E2",
          "F2:G2",
          "H2:I2",
          "J2:J3",
          "K2:L2",
          "M2:N2",
          "O2:P2"
        ];
        //  const merges = ['A1:A2', 'B1:B2', 'C1:I2','J1:P2']

        excel.export_json_to_excel({
          multiHeader,//这里是第一行的表头
          multiHeader2,//这里是第二行的表头
          header: tHeader,//这里应该是算第三行的表头
          data,
          merges,
          filename: this.filename
        });
        // this.downloadLoading = false
      });
    },
    formatJson(filterVal, jsonData) {
      return jsonData.map(v =>
        filterVal.map(j => {
          if (j === "timestamp") {
            return parseTime(v[j]);
          } else {
            return v[j];
          }
        })
      );
    },




    },

Export2Excel.js，在此文件进行修改，

export function export_json_to_excel({
  multiHeader = [],
  multiHeader2 = [],//第三个参数
  header,
  data,
  filename,
  merges = [],
  autoWidth = true,
  bookType = 'xlsx'
} = {}) {
  /* original data */
  filename = filename || 'excel-list'
  data = [...data]
//此处是第三行行表头
  data.unshift(header);
//此处是第二行表头
  for (let i = multiHeader2.length - 1; i > -1; i--) {
    data.unshift(multiHeader2[i])
  }
//此处是第一行行表头
  for (let i = multiHeader.length - 1; i > -1; i--) {
    data.unshift(multiHeader[i])
  }

Export2Excel.js  (全部代码，此文件是我修改后的)，如下：

/* eslint-disable */
import { saveAs } from 'file-saver'
import XLSX from 'xlsx'

function generateArray(table) {
  var out = [];
  var rows = table.querySelectorAll('tr');
  var ranges = [];
  for (var R = 0; R < rows.length; ++R) {
    var outRow = [];
    var row = rows[R];
    var columns = row.querySelectorAll('td');
    for (var C = 0; C < columns.length; ++C) {
      var cell = columns[C];
      var colspan = cell.getAttribute('colspan');
      var rowspan = cell.getAttribute('rowspan');
      var cellValue = cell.innerText;
      if (cellValue !== "" && cellValue == +cellValue) cellValue = +cellValue;

      //Skip ranges
      ranges.forEach(function (range) {
        if (R >= range.s.r && R <= range.e.r && outRow.length >= range.s.c && outRow.length <= range.e.c) {
          for (var i = 0; i <= range.e.c - range.s.c; ++i) outRow.push(null);
        }
      });

      //Handle Row Span
      if (rowspan || colspan) {
        rowspan = rowspan || 1;
        colspan = colspan || 1;
        ranges.push({
          s: {
            r: R,
            c: outRow.length
          },
          e: {
            r: R + rowspan - 1,
            c: outRow.length + colspan - 1
          }
        });
      };

      //Handle Value
      outRow.push(cellValue !== "" ? cellValue : null);

      //Handle Colspan
      if (colspan)
        for (var k = 0; k < colspan - 1; ++k) outRow.push(null);
    }
    out.push(outRow);
  }
  return [out, ranges];
};

function datenum(v, date1904) {
  if (date1904) v += 1462;
  var epoch = Date.parse(v);
  return (epoch - new Date(Date.UTC(1899, 11, 30))) / (24 * 60 * 60 * 1000);
}

function sheet_from_array_of_arrays(data, opts) {
  var ws = {};
  var range = {
    s: {
      c: 10000000,
      r: 10000000
    },
    e: {
      c: 0,
      r: 0
    }
  };
  for (var R = 0; R != data.length; ++R) {
    for (var C = 0; C != data[R].length; ++C) {
      if (range.s.r > R) range.s.r = R;
      if (range.s.c > C) range.s.c = C;
      if (range.e.r < R) range.e.r = R;
      if (range.e.c < C) range.e.c = C;
      var cell = {
        v: data[R][C]
      };
      if (cell.v == null) continue;
      var cell_ref = XLSX.utils.encode_cell({
        c: C,
        r: R
      });

      if (typeof cell.v === 'number') cell.t = 'n';
      else if (typeof cell.v === 'boolean') cell.t = 'b';
      else if (cell.v instanceof Date) {
        cell.t = 'n';
        cell.z = XLSX.SSF._table[14];
        cell.v = datenum(cell.v);
      } else cell.t = 's';

      ws[cell_ref] = cell;
    }
  }
  if (range.s.c < 10000000) ws['!ref'] = XLSX.utils.encode_range(range);
  return ws;
}

function Workbook() {
  if (!(this instanceof Workbook)) return new Workbook();
  this.SheetNames = [];
  this.Sheets = {};
}

function s2ab(s) {
  var buf = new ArrayBuffer(s.length);
  var view = new Uint8Array(buf);
  for (var i = 0; i != s.length; ++i) view[i] = s.charCodeAt(i) & 0xFF;
  return buf;
}

export function export_table_to_excel(id) {
  var theTable = document.getElementById(id);
  var oo = generateArray(theTable);
  var ranges = oo[1];

  /* original data */
  var data = oo[0];
  var ws_name = "SheetJS";

  var wb = new Workbook(),
    ws = sheet_from_array_of_arrays(data);

  /* add ranges to worksheet */
  // ws['!cols'] = ['apple', 'banan'];
  ws['!merges'] = ranges;

  /* add worksheet to workbook */
  wb.SheetNames.push(ws_name);
  wb.Sheets[ws_name] = ws;

  var wbout = XLSX.write(wb, {
    bookType: 'xlsx',
    bookSST: false,
    type: 'binary'
  });

  saveAs(new Blob([s2ab(wbout)], {
    type: "application/octet-stream"
  }), "test.xlsx")
}

export function export_json_to_excel({
  multiHeader = [],
  multiHeader2 = [],
  header,
  data,
  filename,
  merges = [],
  autoWidth = true,
  bookType = 'xlsx'
} = {}) {
  /* original data */
  filename = filename || 'excel-list'
  data = [...data]
  data.unshift(header);
  for (let i = multiHeader2.length - 1; i > -1; i--) {
    data.unshift(multiHeader2[i])
  }
  for (let i = multiHeader.length - 1; i > -1; i--) {
    data.unshift(multiHeader[i])
  }

  var ws_name = "SheetJS";
  var wb = new Workbook(),
    ws = sheet_from_array_of_arrays(data);

  if (merges.length > 0) {
    if (!ws['!merges']) ws['!merges'] = [];
    merges.forEach(item => {
      ws['!merges'].push(XLSX.utils.decode_range(item))
    })
  }

  if (autoWidth) {
    /*设置worksheet每列的最大宽度*/
    const colWidth = data.map(row => row.map(val => {
      /*先判断是否为null/undefined*/
      if (val == null) {
        return {
          'wch': 10
        };
      }
      /*再判断是否为中文*/
      else if (val.toString().charCodeAt(0) > 255) {
        return {
          'wch': val.toString().length * 2
        };
      } else {
        return {
          'wch': val.toString().length
        };
      }
    }))
    /*以第一行为初始值*/
    let result = colWidth[0];
    for (let i = 1; i < colWidth.length; i++) {
      for (let j = 0; j < colWidth[i].length; j++) {
        if (result[j]['wch'] < colWidth[i][j]['wch']) {
          result[j]['wch'] = colWidth[i][j]['wch'];
        }
      }
    }
    ws['!cols'] = result;
  }

  /* add worksheet to workbook */
  wb.SheetNames.push(ws_name);
  wb.Sheets[ws_name] = ws;

  var wbout = XLSX.write(wb, {
    bookType: bookType,
    bookSST: false,
    type: 'binary'
  });
  saveAs(new Blob([s2ab(wbout)], {
    type: "application/octet-stream"
  }), `${filename}.${bookType}`);
}

希望对大家有帮助，不懂的请留言或私信我。