Depends how you buy the ticket. e.g. If your final destination is Guangzhou (CAN),
sailor(Ocean & Mountain)
you buy one single ticket from YYZ to CAN, with two legs YYZ-PEK and PEK-CAN, then no problem with the baggage; However, if you buy two separate tickets as YYZ-PEK and PEK-CAN, then the part from PEK-CAN would subject to domestic baggage rules.