My work permit will expire on 30 Semptember. I find a new job in canada.
Normally, I should apply new work permit in Canada. But I want to come back to China for two months. Can I apply for a new work visa in China? Can I get the new work permit at the vancouver airport just like when I first come to Canada before?

You can apply for the new work permit in China; it is not certain that the case would be concluded withing two months, but once it is, you would collect the work permit at the port of entry upon arrival in Canada.