I am sponsoring my wife while living in china with her, I am here on a multiple entry family visiting visa. Should I put my address in canada or in china on the application?
If you are planning to be going in and out of China visiting her - maybe for a month at a time, then two months back in Canada, then another visit, and so on - then state your Canadian address as your address, and include evidence of all these visits as part of the proof your relationship is genuine.
But I got the impression you were planning on staying in China for the whole time it takes to process the visa - which for Hong Kong can be a long time - so even if you are on a tourist visa, if you are actually living there, put your Chinese address as your residential address. For one thing, actually living together is good evidence that the relationship is genuine, so you want to be sure that you can prove you are living together.
For the mailing address, use the address where you want to receive mail. If your Canadian address is your parents' house, they can get your mail from CIC for you, and then forward it to you, scan and email it, or tell you right away what it is over the phone. You could also use your Chinese address if the mail in the area you live in is reliable - where I lived in China only about one out of every three letters mailed to me actually got to me; the rest vanished.