Generally, the free luggage allowance is 40kg for the first class; 30kg for the business class and 20kg for the economy class. And there are also some specific provisions for the hand baggage. It is hard to describe it clearly in one or two sentences; you can refer to the 'about luggage' column on the page https://www.travelchinaguide.com/china-flights/booking-faqs/ for details.