I just start to learn python and web2py. Because of web2py's web interface development, I am wondering how can web2py work with svn? If a team wants to build a website,how do they work together? How to control the iteration of source code?
Yes, it works fine with svn, hg, whatever source control you need to use. 
Sometimes people think that you have to code with web2py's admin interface, but that really is not the case, once you realize it can be edited with any of your regular tools, you will see that you don't have to treat it any differently when it comes to source control either.
If you use the source version of web2py, you'll have a single folder on disk that contains an entire web2py application server (that in turn contains your 'application' folders). Just check that whole folder into source control. 
Now, on the machine that is running web2py, you can make changes either with web2py's web interface, or by just editing the python files directly with another editor (I use WingIDE for example). You'll have the normal svn update/modify/commit cycle at this point. 
If multiple people are editing code using web2py's admin interface, all of their changes will be made on the machine running web2py... just periodically do a commit from that system and you are all set.
Using the admin interface to modify the source code is convenient, but for for bigger changes, each member of your team should have their own local copy of the svn branch. They make changes to their local files and commit them. Then from the server running web2py, just do an 'svn up' to get modifications from the rest of the team.
Can web2py work with svn?