Abstract: The frequency and characteristics of different intensity precipitation caused by all kinds of clouds were analyzed in the demonstration region of artificial precipitation enhancement in Liaoning Province during May to October from 1989 to 1999.The results showed that the precipitation duration had a negative exponential function relationship with corresponding precipitation frequency.The longer the precipitation duration was,the less the precipitation frequency was.The precipitation duration and precipitation distribution showed an irregular fluctuation.The 2-8 hours precipitation duration in which the precipitation accounted for 66% to total precipitation was the best period of precipitation enhancement.