Objective To analyze the prevalence and clinical features of cytomegalovirus (CMV)infection in patients with systemic lupus erythematosus (SLE).Methods Patients with SLE in Peking University Third Hospital from 2013 to 2015 and age and sex matched healthy controls were enrolled.All patients were detected for CMV antibody,CMV DNA and CMV PP65 in the blood.The prevalence of CMV infection and the clinical characteristics were analyzed using Chi-square test.Results Altogether 349 SLE patients and 209 healthy controls were enrolled.In SLE group,the positive rate of CMV IgG was 90.3％ (315/349),which was similar to that of the control group,while the positive rate of CMV IgM was 8.0％ (28/349),which wassignificantly higher than controls 1.4％(3/209) (x2=10.811,P=0.001),and the active CMV infection rate was 69.1％(241/349).Those in the active phase of SLE were more likely to have active CMV infection when compared with those in remission [75.4％(93/256) vs 51.6％(48/93),x2=18.049,P＜0.01].The percentage [43.2％(104/241)] of severe patients in those with active CMV infection was much higher than that in those without CMV infection 9.2％(10/108) (x2=38.953,P＜0.01).Those SLE patients had active CMV infection were clinically more severe and the most common clinical manifestation were proteinuria/hemoturia,cytopenia and fever.Conclusion In SLE patients,the positive rate of CMV IgM is significantly higher than healthy control and the prevalence of active CMV infection is high,especially in those at active disease.Those with active CMV infection are clinically more severe but have no features of active CMV infection,which indicates that the CMV infection might be a trigger of SLE activity.