Aimed at the pollution problem of fish cage culture,the paper used water quality model to simulate and predict the pollution problem of fish cage cultur. Fish cage culture pollution in the Panjiakou Reservoir was generalized to surface source load, and the calibrated QUAL2Kw model was applied for fish cage culture pollution in the Panjiakou reservoir both before and after banning cage cultures,and used root mean square meters (RMSE) to carry out applicability evaluation for QUAL2Kw model.The influence of different pollution sources on water quality at outlet was assessed by the improved QUAL2Kw model with pollutant load ratios and contribution ratio modules. The results show that the QUAL2Kw model has good adaptability and can provide a reliable model foundation to simulate and analyze fish cage culture pollution problems in the Panjiakou Reservoir; if fish cage culture is banned, the concentrations of constituents would decrease finitely. To improve water quality of Panjiakou Reservoir at outlet. It is more effective to reduce pollutant load between S6 to S7. The method can provide the scientific basis and decision support for the water environmental management of Panjiakou reservoir.