As to the main source of non point source pollution in western region of Taihu Basin,the output coefficient was got according to the relationship between the unit field experiment and the monitoring values of small watershed nutrient output and the structure of watershed land use. The emissions of COD、TN、NH3 N and TP from typical land use of planting industry were calculated. Combined with those emissions of other kinds of non point source pollution, the authors of this paper thought that the non point source pollution in the western region of Taihu Basin was mainly from rural sewage and planting industry pollution. The main problems existing in controlling different types of non point source pollution were analyzed. On this basis, some treatment mode for controlling non point source pollution were proposed,aiming to provide a reference for non point source controlling in Taihu Lake watershed.