Abstract: A mathematical model was developed to simulate the terrain effect on meterology parameter when cold-air flow passing over a mountain terrain. The solar short-wave radiation, ground and atmolphere long-wave radiation, soil heat flux, the diffusion and transport of water vapor, heat and momentum fluxes in the atmosphere' and the Coriolis parameter change with latitude were considered in the model. The resonable phenomena were obtaioned, such as, wind field change, temperature decrease, the abrupt increase of flux and pressure increase etc. The model provides a method and basis for weather forcast and the reseaech of mesoscale processes over complex terrain.