Abstract: Based on the basic dynamic frame of an operational model(KMM 3),a new meso scale NWP model with good considerations of many physical processes is designed.In the model,(x,y,σ) coordinates system is used,several boundary arrangements are supplied and model resolution can be chosen with ease.The precipitation includes contributions of both large scale process and deep convective process.Ground surface temperature is computed from surface energy budget equation.The exchanges between ground and atmosphere and from ocean to atmosphere are considered.The drag coefficients are calculated with liouis scheme and the exchange coefficients in PBL are calcuated with a scheme similar to that of Liouiss.Two types of horizontal diffusion scheme,the second order form and the fourth order form,are used here.The model is integrated with an economical time differencing system.With 80 kilometers taken as the mesh interval and model atmosphere divided into 16 layers,26 prediction experiments are made.The results show that,the model runs stably with good efficiency,well predicting the main resovable meso scale systems and large scale patterns and the precipitation predicted is close to the real case.