conversion of water substance in clouds, and precipitation efficiency were simulated. The model simulation declared that plen tiful vapor inflow provided a favorable condition for the formation and developm ent of clouds. The inflow of vapor in the Henan region was mostly horizontal wit h weak contribution from surface evaporation. The main vapor inflow exists in th e southern and western sides of Henan with the strongest inflow at about the hei ght of 2 km, whereas the eastern and northern sides are main vapor outflow. The average height of 0℃ layer is about 2.5km. The clouds have a distinct verti ca llylayered structure with ice cloud above 6 km, waterice mixed cloud betwee n 2.5～6km, and liquid cloud below 2.5km, which accords with the “seeder feed er" cloud structure. The horizontal flow of hydrometeor was weaker compared with the vapor flow. The growth of precipitating ice particles mainly occurs at about the height of 4km, and that of rain droplets at about the height of 2.5km, where is near the zero temperature level. The temporal change of regional hourly preci pitation efficiency is consistent with surface hourly precipitation with a disti nct lag behind the vapor inflow. During strong precipitation, regional hourly pr ecipitation efficiency is 20%～30%. The distribution of regional precipitation e fficiency is consistent with total precipitation with higher value in the southe rn Henan and lower value in the north.