Abstract: Objective To examine the prevalence rate and distribution characteristics of severe mental diseases(SMDs)in Gansu province and to provide a basis for community prevention and rehabilitation of the diseases.Methods A survey on SMDs was carried out among all permanent community residents in Gansu province with trace survey and cluster sampling from April through September 2015.International Statistical Classification of Disease and Related Health Problems,10th Revision (ICD-10)and Chinese Classification and Diagnostic Criteria of Mental Disorders,3th Revision(CCMD-3)were adopted as diagnostic criteria in the survey.SPSS 19.0 was used in data analysis.Results By the end of the survey,totally 47 215 cases of SMDs were identified,with an overall prevalence rate of 1.832‰ and a prevalence rate of 1.339‰ for schizophrenia;the difference in the prevalence rates of various SMDs was statistically significant(χ²=109 928.571,P=0.000).The prevalence of SMDs in rural residents (2.483‰)was significantly higher than that in the urban residents (0.803‰)(χ²=9 441.793,P=0.000).The overall prevalence rate of SMDs in the male residents (1.877‰)was significantly higher than that in the female residents (1.784‰)(χ²=30.250,P=0.000).The prevalence of mental development retardation comorbid with mental disorder and mental disorder due to epilepsy in the male residents were significantly higher than those in the female (χ²=326.274,P=0.000 and χ²=120.624,P=0.000);whereas the prevalence of bipolar affective disorder and schizoaffective disorder in the male residents were significantly lower than those in the female (χ²=24.590,P=0.000 and χ²=30.218,P=0.000).Of the SMDs cases identified,27.1% were aged 46-55 years;94.6% were Han nationality;44.1% had the education of primary school or below;55.9% were married;and 79.5% were farmer.Conclusion Schizophrenia is a major disease for the prevention and treatment of SMDs among community residents in Gansu province and specific measures for prevention and treatment of SMDs should be implemented in various populations,particularly in rural populations.