After immigrating to Canada or Australia, if you are naturalized, does the property in China need to be included in the tax of the country of nationality?

Joining Canadian citizenship means giving up China citizenship automatically, and you need to apply for a visa next time you return to China. As you are no longer a citizen of China, you can't be a civil servant in China.

But I've never heard of China's property being taxed.

This is your overseas property, and you can choose not to declare it.