Most hotels in China that cater to international travellers provide an in-room safe or a front-desk safe, and these are generally reliable for passports, cash, and electronics. Still, safes vary in quality and policy, so confirm what your specific hotel offers and never assume absolute security.
When you arrive at a hotel in China, the front desk will scan your passport into a government registration system before you get a room key. That scan is not optional paperwork — it is a legal requirement for every foreign guest, and it is the exact moment that decides whether a property is allowed to host you. Most international and mid-range hotels finish it in seconds; some budget places cannot do it at all, which is why they turn foreigners away.