During the design of artificial lake, the water quality is deteriorated to a certain degree so that water diversion must be applied to exchange the old water to ensure the water quality. If the design is not scientific, it will cause a great waste of water resource. Taking Zhengding Lake for example, based on EFDC, the paper analyzed the simulation state of tracer particles in the lake in different schemes of water diversion, determined the optimum scale of water transfer according to the simulative results of tracer particles, and ascertained the potential region of heavy pollution and the region of eutrophication, which supplied technical support for the guarantee of water environmental quality in the lake area.