Abstract: It was difficult for the Xiao'anxi River Basin in Western Chongqing to reach the standard of water environment quality. According to the monitoring section of municipal control,the pollution carrying area units were divided. Based on the results of pollution source investigation and monitoring,the emission and pollution load of pollution sources in each unit were analyzed. The results showed that the COD load was 23103. 94 tons,the ammonia nitrogen load was 1049. 63 tons,and the total phosphorus load was 325. 74 tons; the main over standard factors of water quality in the Xiao'anxi basin were COD and total phosphorus,while the agricultural source was the main source,the livestock and poultry breeding pollution was the main problem affecting the water quality of the basin;the living source and centralized pollution source also had a large impact on the water quality. However,the industrial source discharge had little impact on the water quality. By identifying the main water environment problems,the countermeasures and suggestions for pollution control were put forward.