It depends on which airlines you will take. Generally, an economy class adult ticket holder is allowed to bear 20 kg for free (checked and carry-on luggage). And for China Southern Airlines, the charge rate of the excess luggage is 1.5% of the full economy class ticket price per kilogram.

Like Mr.Keelm said it depends of what airline you take. It is usally either 20 or 23kg checkin in baggage and 5 or 7 kg carry-on baggae for free. For China Southern Airlines its 20kg for discounted economy and 30 for full-priced economy.