According to the document , I have setted the property:"stateful" , "stateId" and added the code below when ExtJs loaded:

Ext.state.Manager.setProvider(new Ext.state.CookieProvider({
expires: new Date(new Date().getTime()+(1000*60*60*24*7)), //7 days from now

The state of grid saved successfully when the whole page reload, but when I instance a new Grid at the same page, the state not save, how to fix it ? Thanks!