Until the end of 2005,twenty-seven drags targeted to the human immunodeficiency virus (HIV) have been approved by the U.S.Food and Drug Administration (FDA).Although great progress has been made in the treatment of this infection by the introduction of highly active antiretroviral therapy (HAART),the high error rote of the reverse transcriptase leads to the emergence of drug resistant strains.Now,HIV infections represent a major medical problem in the world.Therefore,development of safe and effective anti-HIV drugs is extremely urgent for the chemotherapy and/or prophylaxis of HIV infection.Three enzymes play the key roles in the life cycle of HIV,the pathogen of AIDS.