The average annual precipitation of Taihu Lake is 950-1000mm on NE shores, which increases to 1200-1250mm on SW shores progressively. The annual precipitation course is characterized by a double-peak model with the maximum value being 147-105mm at all stations in Jun. and the minimum value 33-l8mm on the most stations in Dec.. The estimated precipitation effect of Taihu Lake shows that there exists a low value region of precipitation on the lake surface fundamentally. The precipitation effect of Taihu Lake enables the precipitation on lake shores to average 20mm less than that of far from the lake shores, <3% of the annual precipitation. This means that the influence of Taihu Lake on the precipitation is not evident, but it has a little impact on the precipitation distribution of this region. The precipitation on the Taihu Lake region is one of the decisive factors of the water level fluctuation.