Upgrading drupal 8 beta3 to beta4 table user__roles not exists When I upgrade my drupal site to beta4 release, it says that table user__roles is not exits.

It's look like that new beta version alter table name from users_roles to user__roles. how is possible to apply this change (How is possible to migrate schema of drupal to latest version).

Thanks.
There is no upgrade path yet.

You could try to alter the table manually, or copy it from a new install, but you will very likely run into other issues as well.