I never had a problem with carry ons in China so far, (even 3 pieces because my checked in weight was too much). But be aware: If you carry on bottles or cans with liquids they will open them to check if they are alcohol free. If they are not, you can't bring them.
And: If you fly out of Hong Kong, the carry on policy is strictly enforced. If the piece doesn't fit into the box you need a special permit from the airline. A second piece would also need a permit tag from the airline unless it is a laptop or a camera. (First and business class + 1 piece)