Abstract: Objective To examine the prevalence and influencing factors of late diagnosis of HIV infection among men who have sex with men(MSM)reported in Minhang District. Methods Through the national system for Comprehensive AIDS Prevention and Control, all newly reported HIV cases infected via homosexual transmission, during January 2005 to December 2015 in Minhang District of Shanghai were included for the present analysis. There were 47 cases excluded for the initial CD4⁺ T cell countdelayed by more than three months after the first HIV positive test. A total of 319 eligible patients were included in this study. Results A total of 103 cases (32.3%) were found to be late diagnosis. Multiple logistic regression analysis indicated that aged over 50 years, cases found from other ways(including detection of floating population, other patients preoperative examination, special survey etc.) were associated with delayed diagnosis of HIV infection, with the OR(95%CI)12.31(1.12-135.67),1.94(1.08-3.50) respectively. Conclusion The prevalence of delayed diagnosis of HIV infection in Minhang District during 2005 to 2015 is at a relatively high level. Age and sample origin are important influencing factors associated with late diagnosis. Continuous efforts for promotion of HIV tests and health education among MSM, people over 50 years are needed to raise the awareness of voluntary counseling and testing.