1.首先安装包：

npm i bpmn-js

安装bpmn-js-properties-panel、activiti-bpmn-moddle：

修改package.json：

"bpmn-js-properties-panel": "https://github.com/RubyLinT/bpmn-js-properties-panel.git",

 "activiti-bpmn-moddle": "https://github.com/igdianov/activiti-bpmn-moddle.git",

npm i 

2.使用实例：

<template>
  <div class="containers" ref="content">
    <div class="canvas" ref="canvas"></div>
    <div id="js-properties-panel" class="panel"></div>
    <ul class="buttons">
      <li>下载</li>
      <li>
        <a ref="saveDiagram" href="javascript:" title="download BPMN diagram">BPMN diagram</a>
      </li>
      <li>
        <a ref="saveSvg" href="javascript:" title="download as SVG image">SVG image</a>
      </li>
    </ul>
  </div>
</template>

<script>
// 引入相关的依赖
// import BpmnViewer from 'bpmn-js'
import BpmnModeler from 'bpmn-js/lib/Modeler'
import propertiesPanelModule from 'bpmn-js-properties-panel'
import propertiesProviderModule from 'bpmn-js-properties-panel/lib/provider/activiti'
import activitiModdleDescriptor from 'activiti-bpmn-moddle/resources/activiti'

export default {
  data () {
    return {
      // bpmn建模器
      bpmnModeler: null,
      container: null,
      canvas: null,
      xmlStr: null,
      processName: ''
    }
  },
  methods: {
    createNewDiagram () {
      const bpmnXmlStr = `<?xml version="1.0" encoding="UTF-8"?>
        <definitions xmlns="http://www.omg.org/spec/BPMN/20100524/MODEL" xmlns:bpmndi="http://www.omg.org/spec/BPMN/20100524/DI" xmlns:omgdc="http://www.omg.org/spec/DD/20100524/DC" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" id="sid-38422fae-e03e-43a3-bef4-bd33b32041b2" targetNamespace="http://bpmn.io/bpmn" exporter="bpmn-js (https://demo.bpmn.io)" exporterVersion="6.0.4">
          <process id="Process_1" isExecutable="true">
            <startEvent id="StartEvent_1acpsqt" />
          </process>
          <bpmndi:BPMNDiagram id="BpmnDiagram_1">
            <bpmndi:BPMNPlane id="BpmnPlane_1" bpmnElement="Process_1">
              <bpmndi:BPMNShape id="StartEvent_1acpsqt_di" bpmnElement="StartEvent_1acpsqt">
                <omgdc:Bounds x="152" y="82" width="36" height="36" />
              </bpmndi:BPMNShape>
            </bpmndi:BPMNPlane>
          </bpmndi:BPMNDiagram>
        </definitions>`
      // 将字符串转换成图显示出来
      this.bpmnModeler.importXML(bpmnXmlStr, function (err) {
        if (err) {
          console.error(err)
        }
      })
    },
    // 下载为SVG格式,done是个函数，调用的时候传入的
    saveSVG (done) {
      // 把传入的done再传给bpmn原型的saveSVG函数调用
      this.bpmnModeler.saveSVG(done)
    },
    // 下载为SVG格式,done是个函数，调用的时候传入的
    saveDiagram (done) {
      // 把传入的done再传给bpmn原型的saveXML函数调用
      this.bpmnModeler.saveXML({ format: true }, function (err, xml) {
        done(err, xml)
      })
    },
    // 当图发生改变的时候会调用这个函数，这个data就是图的xml
    setEncoded (link, name, data) {
      // 把xml转换为URI，下载要用到的
      const encodedData = encodeURIComponent(data)
      // 获取到图的xml，保存就是把这个xml提交给后台
      this.xmlStr = data
      // 下载图的具体操作,改变a的属性，className令a标签可点击，href令能下载，download是下载的文件的名字
      if (data) {
        link.className = 'active'
        link.href = 'data:application/bpmn20-xml;charset=UTF-8,' + encodedData
        link.download = name
      }
    }
  },
  mounted () {
    // 获取到属性ref为“content”的dom节点
    this.container = this.$refs.content
    // 获取到属性ref为“canvas”的dom节点
    const canvas = this.$refs.canvas

    // 建模，官方文档这里讲的很详细
    this.bpmnModeler = new BpmnModeler({
      container: canvas,
      // 添加控制板
      propertiesPanel: {
        parent: '#js-properties-panel'
      },
      additionalModules: [
        // 左边工具栏以及节点
        propertiesProviderModule,
        // 右边的工具栏
        propertiesPanelModule
      ],
      moddleExtensions: {
        activiti: activitiModdleDescriptor
      }
    })

    // 下载画图
    let _this = this
    // 获取a标签dom节点
    const downloadLink = this.$refs.saveDiagram
    const downloadSvgLink = this.$refs.saveSvg
    // 给图绑定事件，当图有发生改变就会触发这个事件
    this.bpmnModeler.on('commandStack.changed', function () {
      _this.saveSVG(function (err, svg) {
        _this.setEncoded(downloadSvgLink, 'diagram.svg', err ? null : svg)
      })

      _this.saveDiagram(function (err, xml) {
        _this.setEncoded(downloadLink, 'diagram.bpmn', err ? null : xml)
      })
    })

    this.createNewDiagram(this.bpmnModeler)
  }
}
</script>

<style lang="scss">
  /*左边工具栏以及编辑节点的样式*/
  @import 'bpmn-js/dist/assets/diagram-js.css';
  @import 'bpmn-js/dist/assets/bpmn-font/css/bpmn.css';
  @import 'bpmn-js/dist/assets/bpmn-font/css/bpmn-codes.css';
  @import 'bpmn-js/dist/assets/bpmn-font/css/bpmn-embedded.css';
  /*右边工具栏样式*/
  @import 'bpmn-js-properties-panel/dist/assets/bpmn-js-properties-panel.css';
  .containers{
    position: absolute;
    background-color: #ffffff;
    width: 100%;
    height: 90%;
  }
  .canvas{
    width: 100%;
    height: 100%;
  }
  .panel{
    position: absolute;
    right: 0;
    top: 0;
    width: 300px;
  }
  .buttons{
    position: absolute;
    left: 20px;
    bottom: 20px;
    &>li{
      display:inline-block;margin: 5px;
      &>a{
        color: #999;
        background: #eee;
        cursor: not-allowed;
        padding: 8px;
        border: 1px solid #ccc;
        &.active{
          color: #333;
          background: #fff;
          cursor: pointer;
        }
      }
    }
  }
</style>