A passport and visa ensured by a Chinese Embassy or Consulate before you arrive in the country. Entry visas can't be ensured at the airport.
To enter China, your passport must be valid for at least 6 months from the date when you made the visa application and has many blank pages. The visa should be approved prior to entering China and a permit for Tibet must be obtained 15 days before entering Tibet. If you only plan to travel and stay in Hong Kong you are exempted from applying for a Chinese visa.