Abstract: Objective To learn the status quo of the HIV/AIDS patients disclosure of HIV status to their regular sex partners in Lancang county, Yunnan province, and investigate the influential factors, providing the basis for improving disclosure of HIV serostatus to sex partners and reducing HIV/AIDS patients risk behaviors. Methods A cross-sectional study was conducted in Lancang County from April to August 2009 to investigate and analyze the HIV/AIDS patients disclosure of HIV status to their regular sex partners. Results Among 283 HIV/AIDS patients, 61.48% have revealed serostatus to their regular sex partners, of which 73.56% were disclosed in person, 17.24% were disclosed by CDC staff with the patients consent, and 3.45% were divulged by CDC staff without consent. The main reasons for informing sex partners of HIV status were: the other side has known, hoping to be understood and loved, and the other side is also infected; while the main reasons for non-disclosure were: being afraid of relationship breakdown, being afraid of discrimination, and not knowing how to communicate with the other. Multivariate Logistic regression analysis showed that the difference in disclosure of HIV status was significant between HIV-positive patients of different educational levels, those who were and were not major economic supporter of the family, and those with and without other persons presence during disclosure. Conclusion To encourage disclosure of HIV status to sex partners, it is important to gradually improve the socio-economic situation for HIV-infected and AIDS patients, raise the social, familial and HIV patients awareness of AIDS, and strengthen the service quality of health care workers in counseling, testing and treatment.