主要就是gridIndex: 1和xAxisIndex: 1,yAxisIndex: 1.

option = {
    title: {
        text: 'Step Line'
    },
    tooltip: {
        trigger: 'axis'
    },
    legend: {
        data: ['Step Start', 'Step Middle', 'Step End']
    },
    grid: [{

        bottom: "50%",
        containLabel: true
    }
    ,
    {

        top: '60%',
        containLabel: true
    
    }],
    toolbox: {
        feature: {
            saveAsImage: {}
        }
    },
    xAxis: [{
        type: 'category',
        data: ['Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat', 'Sun'],
        
    },
    {
        type: 'category',
        data: ['Mon', 'Tue', 'Wed', 'Wed', 'Fri', 'Sat', 'Sun'],
        gridIndex: 1
    }],
    yAxis: [{
        type: 'value'
    },{
        type: 'value',
        gridIndex: 1
    }],
    series: [
        {
            type: 'line',
            data: [120, 132, 101, 134, 90, 230, 210]
        },
        {
            type: 'line',
            // step: 'middle',
            data: [220, 282, 201, 234, 290, 430, 410]
        },
        {
            type: 'line',
            data: [450, 432, 401, 454, 590, 530, 510],
            
        },
        {
            name: 'Step Start',
            type: 'line',
            // step: 'start',
            data: [120, 132, 101, 134, 90, 230, 210],
            xAxisIndex: 1,
            yAxisIndex: 1
        },
        {
            type: 'line',
            data: [220, 282, 201, 234, 290, 430, 410],
            xAxisIndex: 1,
            yAxisIndex: 1
        },
        {
            type: 'line',
            data: [450, 432, 401, 454, 590, 530, 510],
            xAxisIndex: 1,
            yAxisIndex: 1
            
        }
    ]
};

效果图：