Abstract: In 2005, the first edition of the guidelines for the diagnosis and treatment of acquired immunodeficiency syndrome(AIDS) was formulated by the AIDS Professional Group of the Society of Infectious Diseases of Chinese Medical Association, which was updated in 2011, 2015, and 2018, respectively. The 2021 edition of the guidelines was revised on the basis of the fourth edition and updated according to the national clinical practice and the latest research results. The new research progress in opportunistic infections, antiretroviral therapy, post-exposure prophylaxis (PEP), pre-exposure prophylaxis (PrEP), the whole course of the management of HIV infection, and prevention of mother to child transmission was updated in these guidelines. In the 2021 edition, the indications, medication regimen, follow-up and monitoring, and precautions of PrEP are introduced in detail. This edition of guidelines will be updated regularly according to the latest clinical evidence.