Can I leave the country without buying a return ticket?

Generally this is not possible.

According to the article "Do I need a round-trip air ticket to go abroad" published on the Hualu website on 2024-01-14? It is found that if you join a travel agency's tour group to go abroad, the travel agency usually provides a round-trip air ticket. If you hold the validity of the visa Only those who stay for 3 months or more (generally student visas, work visas, labor visas, study visit visas, immigration visas, and family visit visas have such long stay periods) can leave the country with a one-way ticket.

According to Article 89 of the "Exit and Entry Administration Law of the People's Republic of China": Exit refers to traveling from the mainland of China to other countries or regions, and from the mainland of China to the Hong Kong Special Administrative Region and Macao Special Administrative Region. Administrative region, from mainland China to Taiwan.