The heat and moisture budgets of a storm snow over the Plateau during Dec.of 1997are diagnosed by using the output data from control simulation,the non-hydrostatic mesoscale model MM5V2 of PSU/NCAR,and the equations of heat and moisture budgets.The diagnostic results for the apparent heat source (Q₁) and apparent moisture sink (Q₂) indicate that the positive vertical integrations of the Q₁ and Q₂ are stronger,and their distribution trend is similar,which also accord with the bands of the storm snow.So,the Q₁ and Q₂ of this case is the results of the condensation of vapor and the release of latent heat.An important thermodynamics mechanism of the genesis and development of the storm snow is that apparent heat sources Q₁ is warm in the middle troposphere and relative cool in the upper troposphere.The peak value area of the area averaged vertical profiles of the Q₁ and Q₂ is close,this area is just the level of the condensation of vapor,it is concerned to the drying of the condensation of vapor in transpot belts of vapor.Apparent heat sources Q₁ and apparent moisture sink Q₂ have the same vertical profile which shows that the no convective condensation precipitation is the main factor in the storm snow event.These results provide physical basis for improving and developing meso scale numerical models used to simulate and forecast the storm snow over the Plateau.