ok I've decied to keep the cash hidden in an envelops and store in my money belt. When I leave China, I think I want to do it on this route:

Shanghai-Hong Kong (and then fly out to the U.S. from HK). I won't be returning to Canada but will convert the RMB to USD in HK.

My question is in Shenzhen (point of exit and entry to HK), will the Chinese officials want to check my money belt (if they do, they'll see, what will be at the point close to 40,000RMB). I don't want to deal with that.

Even if they don't check the belt manually, the x-ray (will scan) the belt through their machine, they can identify cash from other materials, right?

Maybe im to worried about nothing.

As long as I take 40,000RMB in Cash from China to Hong Kong and then to the U.S., I'm happy.