The spatial and temporal variations of water quality in Wuxi water area of Taihu Lake are important for regional eutrophication control and water pollution control. Based on the monthly water quality data of Wuxi water area of Taihu Lake and the water quantity data of rivers entering the lake from 2010 to 2020, the spatial and temporal variation characteristics of water quality and eutrophication status of the lake were evaluated using the integrated pollution index and integrated nutrient status index. The inter-annual variation pattern and spatial pattern of major water quality indicators were analyzed, and the correlation between the water quality of the lake and the concentration and flux of pollutants in rivers entering the lake was investigated. The results show that the water quality of Wuxi water area of Taihu Lake improved significantly from 2010 to 2020, and the integrated pollution index and integrated nutrient status index of the whole lake decreased by 25% and 10%, respectively. Except for the concentration of total phosphorus concentration with no obvious change trend, the concentration of other water quality factors in the lake area all showed a downward trend. In terms of seasonal changes, permanganate index, total phosphorus, and chlorophyll-a concentrations maintained higher values in summer and autumn, while total nitrogen and ammonia nitrogen concentrations maintained higher values in winter and spring. Spatially, nutrient concentrations decreased from the northwestern and northern lakes to the southeastern and eastern lakes. The changes in water quality of rivers entering the lake from 2013 to 2020 are basically consistent with the trends of water quality in the lake area. The concentration of total nitrogen and ammonia nitrogen in the lake area are significantly positively correlated with the concentration of total nitrogen in inflow river and the flux of ammonia nitrogen into the lake, respectively. The spatial pattern response is consistent, and the exogenous input of the inflow river is an important factor affecting the spatial and temporal changes of water quality in the lake area.