Abstract: Considering the change of various ecological factors in lake,which effected on the whole phosphorus sediment process,a stochastic difusion model for the total Phosphorus concentration in lake is estabilished,where a standard Brownian motion perturbs the whole phosphorus sediment process. We extend the Vollenweider water quality model and obtain its analytical solution,mean,and variance According to the sediment coefficient,a method that controls the total phosphorus concentration is pointed out. The model is applied to the Chao Lake in Anhui province.