Abstract: Objective To investigate the status and influencing factors of previous and new human immunodeficiency virus (HIV) infection among men who have sex with men (MSM) in Xi'an city.Methods A total of 2 444 MSM were recruited with snow-ball or respondent-driven sampling in Xi'an city;a face-to-face questionnaire survey and 3-5 ml venous blood collection for the determination of HIV immunoglobulin G (IgG) with HIV-1 subtypes B,E and D (BED) capture enzyme immunoassay (BED-CEIA) were conducted among the MSM between 2013 and 2015.Logistic regression model was used to explore the risk factors for HIV infection.Results The average age of the MSM was 28.98±7.54 years.Of the MSM,70.8% were unmarried;81.5% lived in local Xi'an more than 2 years;78.1% had the education level of college or above;and 75.5% were self-identified as a gay.More than a half (50.6%) of the MSM looked for sexual partners via internet and 83.7% of the MSM reported unsafe anal homosexual behavior during previous 6 months.Totally 178 HIV seropositive cases were identified among the MSM,with an infection rate of 7.29%.For the 163 HIV seropositive cases with BED-CEIA,71 (39.9%) were new HIV infections,with an estimated incidence rate of 6.08%.Multivariate logistic regression analysis showed that the abuse of isobutyl nitrite inhalation (Rush) was a risk factor (odds ratioOR=2.082,95% confidence interval 95%CI:1.135-3.820) and taking a test for HIV infection during previous one year was a protective factor (OR=0.234,95%CI:0.131-0.417) for new HIV infection.Conclusion HIV infection rate is still at a high level and regular test for HIV infection may reduce the incidents of new HIV infection among MSM in Xi'an city.