var viewer = new Cesium.Viewer('cesiumContainer');

var czml = [{
            "id": "document",
            "name": "polygon",
            "version": "1.0"
        }, {
            "id": "shape2",
            "name": "Red box with black outline",
            "availability": "2012-08-04T16:00:00Z/2012-08-04T18:00:00Z",
            "box": {
                "dimensions": {
                    "cartesian": [30.0, 30.0]
                },
                "material": {
                    "stripe": {
                        "orientation": "VERTICAL",
                        "evenColor": {
                            "rgba": [10, 211, 250, 0]
                        },
                        "oddColor": {
                            "rgba": [10, 211, 250, 255]
                        },
                        "offset": {
                            "number": 1
                        },
                        "repeat": 0.5
                    }
                },
            },
            "path": {
                "material": {
                    "solidColor": {
                        "color": {
                            "interval": "2012-08-04T16:00:00Z/2012-08-04T18:00:00Z",
                            "rgba": [255, 255, 255, 128]
                        }
                    }
                },
                "width": [{
                    "interval": "2012-08-04T16:00:00Z/2012-08-04T18:00:00Z",
                    "number": 3.0
                }],
                "show": [{
                    "interval": "2012-08-04T16:00:00Z/2012-08-04T18:00:00Z",
                    "boolean": true
                }]
            },
            "position": {
                "interpolationAlgorithm": "LAGRANGE",
                "interpolationDegree": 1,
                "epoch": "2012-08-04T16:00:00Z",
                "cartographicDegrees": [
                    0.0, 118.87841653400005, 30.95679870500004, 0.0,
                    10.0, 118.87826541800007, 30.95680770900003, 0.0,
                    20.0, 118.8774481050001, 30.956860625000047, 0.0,
                    30.0, 118.87660414600009, 30.956910105000077, 0.0,
                    ...省略
                ]
            }
        }];

    var dataSourcePromise;
    var i = 30;
    var a = 410;
    setInterval(function() {
        i += 0.001;
        a += 10;
        czml[1].position.cartographicDegrees.push(a, 118.813667, i, 0);
    }, 10000);

    dataSourcePromise = Cesium.CzmlDataSource.load(czml);
    viewer.dataSources.add(dataSourcePromise);
    viewer.zoomTo(dataSourcePromise);

...
setInterval(function() {
    ...
    //路径最后添加节点
    czml[1].position.cartographicDegrees.push(a, 118.8747338, i, 0);
    //清空之前数据，否则数据越来越多
    viewer.entities.removeAll();
    //重新添加修改后的数据
    viewer.dataSources.add(Cesium.CzmlDataSource.load(czml));
}, 1000);

var czml = [{
    "id" : "document",
    "name" : "CZML Path",
    "version" : "1.0",
    "clock": {
        "interval": "2012-08-04T10:00:00Z/2012-08-04T15:00:00Z",
        "currentTime": "2012-08-04T10:00:00Z",
        "multiplier": 10
    }
}, {
    "id" : "path",
    .....
}];

...
//路径最后添加节点
czml[1].position.cartographicDegrees.push(a, 118.8747338, i, 0);
//修改当前时间
czml[0].clock.currentTime = viewer.clock.currentTime.toString();
...