series: [
    {
        name: '数量',
        type: 'bar',
        zlevel: 1,
        itemStyle: {
            normal: {
                barBorderRadius: [0, 30, 30, 0],
                color: (params) => {
                    return new echarts.graphic.LinearGradient(0, 0, 1, 0, [
                        {
                            offset: 0,
                            color: 'rgba(54,69,129,1)',
                        },
                        {
                            offset: 0.8,
                            color: colorList[params.dataIndex],
                        },
                        {
                            offset: 1,
                            color: 'rgba(255,255,255,0.8)',
                        },
                    ]);
                },
                // color: (params) => {
                //   return colorList[params.dataIndex]
                // }
            },
        },
        barWidth: 15,
        data: data1,
    },
    {
        name: '背景',
        type: 'bar',
        barWidth: 15,


                z:"-3",
                barGap: '-75%',
        data: defaultData,
        itemStyle: {
            normal: {
                color: '#1B375E',
                barBorderRadius: [0, 30, 30, 0],
            },
        },
    },
], 

rar

将那个写的柱子宽度设成 0 看下效果， barWidth:0,