I tried to google and found nothing.
Is there any website which show how to implement GWT with PureMVC?
You can start by referring to http://code.google.com/p/purevmc4gwt/ . The project is abandoned with no activity since 2008. There has been massive changes in GWT since and GWT has moved towards a MVP approach to accommodate web-centric optimization. https://developers.google.com/web-toolkit/articles/mvp-architecture
PureMVC also has several attempts with javascript ports. The last one seems to have vanished http://puremvc.org/content/view/156/1/
If you have tried any puremvc javacript ports. You can write JSNI wrappers and utilize them. It will be quite a challenge :)