Special items such as documents, valuables, currency could not be packed in checked luggage when taking China domestic flight. Seeing more details in the following:

Can I keep my documents into my checked luggage?

The answer will be depending on the documents importance.

Don’t put important documents such as your airline invoice, copies of your passports, driving license, and something like that.

Can I put cash into my checked luggage? 

No. Don’t put cash or any currency in your checked luggage. The custom will check your luggage and is not responsible for losing if you doing like that.

Other special items which could not be packed in the check luggage:

Fragile items including painting, china, pottery, or something like that

Valuables including gold and silver wares, watches, jade wares, diamond, etc.