Objective To analyze the clinical characteristics of new onset diffuse type ulcerative colitis.Methods From May 2007 to March 2012,clinical data of hospitalized patients diagnosed in the People's Hospital of Xinjiang Autonomous Region as new onset ulcerative colitis were retrospectively analyzed,and constituent ratios of nationality,gender,age at diagnosis,residential environment,severity of disease,clinical symptoms,results of laboratory examination,results of colonoscopic examination and results of histopathological examination were compared among the diffuse type,the type of proctosigmoiditis and the type of left-sided colitis.Normal distribution data were analyzed by one-way analysis of variance,skew distribution data and ordinal data were analyzed by Kruskal-Wallis H test,and count data were analyzed by chi-square test in the comparison among the three groups.Results A total of 67 patients with new-onset diffuse type ulcerative colitis were enrolled.The constituent ratios of Han nationality,Uygur nationality and Kazak nationality were 32.8％(22/67),58.2％(39/67),and 9.0％(6/67),respectively.The ratio of male to female was 1.48∶ 1.The age at diagnosis was (43.27 ± 16.91) years old.The ratio of city to countryside was 3.19∶ 1.To the severity of the disease,mild was more common,the proportion of mild,moderate and severe were 56.7％(38/67),20.9％(14/67) and 22.4％ (15/67),respectively.Abdominal pain,diarrhea and purulent stools were the predominant symptoms.Some patients might have fever and tenesmus,a few patients accompanied with abdominal distension,nausea,vomiting and peripheral arthritis.The percentage of increasesed erythrocyte sedimentation rate,hypersensitive Creation protein and plasmatic fibrinogen was 37.3％(25/67),44.8％(30/67) and 31.3％ (21/67),respectively.To compare with patients with proctosigmoiditis and left-sided colitis,the patients with new-onset diffuse type colitis had higher Mayo score and were more prone to develop abdominal pain,diarrhea,severe colitis,and were more common in Uygur nationality.There were statistical differences in abdominal pain,diarrhea,severity,ratio of Uygur nationality and Mayo score in pairwise comparison among the three groups (all P＜0.017).Conclusion Abdominal pain,diarrhea and Uygur nationality are more common in new onset diffuse ulcerative colitis in Xinjiang Region,with relatively high Mayo score and mild to moderate degree,while severity significantly increased compared to the type of proctosigmoiditis and the type of left-sided colitis.