Thanks for your reply, Lindalou.
In these days, I am very worried about the thesis. Hope I can pass viva with minor correction. Major modification seems too long for me, now I have to work more hard on my thesis.
Really thanks for your words. That gives me more confidence in next days.
Bless! :$

Today I have a talk with my supervisor. Initially, he plans to hold a viva in Feb 2013. The I tell him my visa expires in Jan 2013. Then he gives me a choice to hold the viva in Dec 2012, and need to submit the thesis in Oct 2012. However, he says that will result in more correction work after viva if submitting in Oct 2012.
I have modified the thesis about three times with the supervisor's comments.
Could anyone give some advise? How can I understand his meaning about more correction if submitting in advance?

Thanks a lot.:-s