primitives.add(new Cesium.Primitive(\{
geometryInstances: ,
releaseGeometryInstances:false,
appearance: new Cesium.PerInstanceColorAppearance()
\}),100);
重点：releaseGeometryInstances:false,
由于Cesium使用primitive加载数据性能考虑，会自动清空原来的geometryInstances，设置即可。