There is no checked luggage service for China bullet train. It means train passengers need to take their luggage to board the train.
Each passenger is allowed to carry 1 - 3 luggage/baggages.
The luggage allowance is 20KG. But usually, it will be OK if your luggage is not exceed 30KG
Each luggage's maximum dimension should not exceed 80*50*40cm.
The luggage racks on both sides overhead the seats. You can put your luggage on it.
If your luggage is too heavy or bigger, you can store your luggage on the racks that are placed at the connection part of two carriages.