Abstract: Objective To explore the condom usage and related factors among men who have sex with men (MSM) at sex with different sexual partners. Methods In-depth interviewing of 43 MSM, recruited from universities, bars, parks, bathing rooms and clubs with commercial sex. Results (1) Nearly half of MSM knew their sexual partners status regarding HIV infection, but they still used condom because of disbelieving. (2) Most MSM used condom at commercial sex,but the use of drug and alcohol before commercial sex or attitude to HIV infection would influence the use of condom. (3) Condom use would be influenced if non-regular sex partners looked attractive. (4) Most of them believed there was no need to use condom at sex with females. (5) The reason for condom use was the fear of HIV infection and the reason for no condom use was the thought that it would influence the pleasant feeling of sex. Conclusion The usage of condom and the influence factors among MSM varied for different sexual partners, so targeted prevention measures should be conducted.