If I immigrate to Canada, can I keep my China citizenship?

Immigration and naturalization are not the same concept.

Immigrants just get permanent residency, which doesn't mean you have become a Canadian citizen. So, you can live in Canada permanently, but you still have China nationality and China passport.

If you apply for naturalization after immigration, you will have Canadian citizenship after passing the naturalization test. From now on, your China nationality is invalid, because China has a single nationality system. Going abroad will hold a Canadian passport, and entry requires a visa.