How to change the authentication classic mode to Claim based authentication

SharePoint 2010 Management shell is the useful tools.
Click start-> all programs -> SharePoint 2010 products -> SharePoint 2010 management shell. Then do as follow:

1. Input $app = Get-SPWebApplication "URL"
2. Input $app.UseClaimsAuthentication, then press Enter, you will see the "false"
3. Input $app.UseClaimsAuthentication = "True", to set the web application use Claims authentication
4. Input $app.Update(), save the changes to database. 

OK, you can use forms based authentication mode.