Abstract: The microphysical processes of unseeded and seeded stratiform clouds in Nanyang of Henan province were simulated in this paper.The results indicated that the ice crystal content showed very low in the natural cloud,and because the ice phase is inactive,it is difficult to form big drops,so the precipitation efficiency is also low.The precipitation intensity had presented two peak values.Through the analysis of unseeded clouds we can obtain the appropriate catalytic site.Generally,the occasion that the cold water content is large,the temperature is low,the clouds maintain stable is the best seed time (simulates the 52 nd minute).Catalyzes on the position for (18 km,18 km,6 km),to spread 0.2 g/s,spreads 1 minute.After adding the ice nucleus in the clouds,the ice crystal content increased rapidly,the rain content decreased correspondingly,with the ice effect become more and more active,the precipitation increased obviously.A high precipitation presented at 148 th minute.This precipitation center achieved its peak value at 150 th minutes.Two precipitation centers were appeared at 172 th minutes.The old precipitation center reached 7 mm/h and the new precipitation center value increased unceasingly,which arrived 16 mm/h at 180 th minutes.That means the rain effect got to its maximum value.