I tried downgrade to the previous version of sourceTree, still have the same problem.
I tried using different username such as jjk will do the commit, but after a while sourceTree give the same error again.
I use command line is working fine with my svn server

here are the errors:
_
git -c diff.mnemonicprefix=false -c core.quotepath=false -c credential.helper=sourcetree svn fetch
Authentication realm: <https://192.168.1.251:8443> VisualSVN Server
Password for 'jinke.jiang':
Authentication realm: <https://192.168.1.251:8443> VisualSVN Server
Username: Use of uninitialized value in concatenation (.) or string at /Applications/SourceTree.app/Contents/Resources/git_local/lib/perl5/site_perl/Git/SVN/Prompt.pm line 20.
Password for '':
Authentication realm: <https://192.168.1.251:8443> VisualSVN Server
Username: Use of uninitialized value in concatenation (.) or string at /Applications/SourceTree.app/Contents/Resources/git_local/lib/perl5/site_perl/Git/SVN/Prompt.pm line 20.
Password for '':
Can't create session: Unable to connect to a repository at URL 'https://192.168.1.251:8443/svn/jinguanjia_ios': No more credentials or we tried too many times.
Authentication failed at /Applications/SourceTree.app/Contents/Resources/git_local/lib/perl5/site_perl/Git/SVN.pm line 143.

Completed with errors, see above_