In this paper, Songjiawan Reservoir is used as an example to evaluate the influence of reservoir construction on water quality, water temperature and groundwater level in both sides of the reservoir area using the one-dimensional water quality complete mixed model, water temperature prediction empirical formula and reservoir area immersion range calculation equation. The results show that when the average annual discharge in wet, flat and dry water year is 16.35m3/s, 6.68m3/s and 2.83m3/s, the pollutant self-purification of the downstream river reaches the water quality standard of the water functional area . The water temperature distribution of the reservoir showed a great difference. The deeper the water is, the lower the water temperature is. The water temperature difference between February and April is large, and the lowest water temperature of the year is 8.28℃, which is 4.42℃ lower than the average surface water temperature of the reservoir. The water temperature on reservoir bottom is similar to that of the surface in October. The water temperature in the reservoir area is relatively stable and basically the same. It is predicted that the infiltration length of two sides of the reservoir is 15.27km 30 years after reservoir construction and the groundwater level is 0.0 to 0.43m higher than before, which shows there is less impact on groundwater. It can provide a scientific basis to prevent and control the effects of water environment and to rationally operate and schedule Songjiawan reservoir.