Changshu City was taken as the study area to explore the response of water quality variation to land use patterns. GIS space technology and SPSS correlation analysis were used to compare land use patterns and total nitrogen (TN) contents in the water body. Results showed that from 1990 to 2010, the areas of farm land and water body decreased continuously, while the areas of construction land and forest land increased. The status index(D_i)of land use pattern was in an order of constructed land>forest>grass land>farmland>water area. The increase in construction land was mainly come from cultivated land and water area, and the reduction of water area is mainly occupied by cultivated land. The area of cultivated land was significantly negatively correlated with the total nitrogen content of the water body (r= -0.959 *, P <0.05), indicating that the proportion of pollution derived from crop-faming was declining. There was no significant correlation between the areas of forest land and grassland and the TN content of the water body. There was a significant positive correlation between the area of construction land and the TN content of the water body (r = 0.929*, P <0.05), indicating that the construction land caused point source pollution.