Abstract: Objective To understand the new infection rate of syphilis and its influencing factors among men who have sex with men （MSM） in Kunming, and to provide reference for comprehensive intervention measures to reduce the syphilis infection among MSM. Methods From June 2018 to December 2020, a prospective, open cohort of MSM was recruited using a combination of Internet, peer referral, and outreach. Questionnaires and serological tests were followed up every 6 months. Univariate and multivariate analyses were conducted by Cox regression model to investigate the influencing factors of new syphilis infection among MSM. Results A total of 198 MSM were enrolled in the cohort．The incidence was 1.36 per 100 person‐year for new syphilis infection. There were significant differences in sexual orientation [HR=4.526 （1.213-112.36）], ways of making friends [HR=4.274 （1.113-56.285）], and whether the subjects had been diagnosed with sexually transmitted diseases in the past year [HR=0.045 （0.005-0.433）] （P<0.05 or P<0.01）. Multivariate Cox regression analysis showed that non‐Internet dating （HR=15.553） and sexually transmitted disease diagnosis in the past year （HR=59.129） were risk factors for syphilis infection among MSM. Conclusions Although the new infection rate of syphilis among MSM is low in Kunming, the risk is still high. A comprehensive intervention model should be adopted to reduce the incidence of syphilis infection.

Key words: Men who have sex with men, Syphilis, Cohort study, New infection