A three-dimensional hydrodynamic and water quality model has been developed for Lake Erhai and its adjacent embayments based on the Environmental Fluid Dynamic Code (EFDC).The model was calibrated and verified by using the field water quality data monitored from 2001 to 2011.The simulated results are in good agreement with observed data,indicating that the model simulation results are accurate and reliable.The model was applied to determine the contributing rate by each waste load inflow at various water quality control points in the lake.The effects of background water quality condition were included in the model in determining the impact of each waste load inflow.The linear programming Simplex Method was used to calculate the optimal loading for each pollutant source with the consideration of constraints on water quality target at different water quality control points in the lake.The allocated pollutant load for Miqie River,Yong'an River and Luoshi River in the northern region of the watershed is the highest due to higher flow discharge,and the amount of allocated loads for total nitrogen,total phosphorus,and COD_Mn from the three rivers takes up to 47%,53% and 49% of the total load for the entire Lake Erhai watershed,respectively.The pollutant load allocation study can be used to facilitate the development of lake pollution control strategies,and to achieve the targeted water quality objectives for Lake Erhai.