A turbine wake model based on mass diffusion for micro-siting of wind farm is proposed.N-S equations and mass diffusion equation are solved to get the data of the field.Polynomial transforms are established to translate the mass concentration distribution into wake equivalent velocity and equivalent turbulent kinetic energy.Experimental data is used to fit the parameters in the transform formula.Besides requiring less computing time，it turns out that the wind turbine wake model based on mass diffusion can change according to the shape of the terrain owning to couple the terrain information through the boundary conditions of concentration equation，which is expected to predict the flow field under the condition of complex terrain.