Abstract: ObjectiveTo explore factors influenceing human immunodeficiency virus (HIV)sero-convertion among HIV-infection discordant couples and to provide evidence for preventing HIV secondary transmission.MethodsHIV-negative couples of HIV-positive patients were investigated from 2006 to 2010 in four counties in Henan province and factors influencing sero-convertion were explored with a case-control study.ResultsUnivariate analysis results showed that education level(χ²=7.298,P=0.026),frequency of sexual activity(χ²=6.075,P=0.048),CD₄⁺T lymphocyte (CD₄)count of HIV positive couple(χ²=10.908,P=0.004),condom use (χ²=52.474,P=0.000),and AIDS prevention related knowledge of the discordant couples (χ²=5.503,P=0.019)were significantly different between case and control group.Multivariate analysis results showed that,compared with the discordant couples using condom in each sexual activity,HIV transmission risk in discordant couples with frequent condom use and seldom condom use was 16.452(95%confidence interval 95%CI=5.837-46.373)and 7.643 (95%CI=2.878-20.296)times higher.CD₄ count> 350 was a protective factor for HIV transmission between the discordant couples and the odds ratio of HIV-infection for CD₄≤200 was 3.224 (95%CI=1.266-8.212)compared to CD₄>350.ConclusionHigh level immune status of the HIV-positive couple and constant condom use are protective factor for prevention of HIV transmission among HIV-infection discordant couples.