Based on the climatic data longer than 20 years, the characteristics of precipitation, including its distribution, variation with altitude and monthly changes are analysed. It may be argued that the variation of anmal precipitation with altitude may be described as a triple curve (one maximum and one minimum appeared in different height). However, in the winter time, it may be described exactly by a quadratic curve (only one maximum height appeared). The "Plateau monsoon has a evident effect on the precipitation distribution of different slopes. Comparing with the surrounding area, the precipitation in the Qinghai lake is reduced in Feb-Jwne and increased by July-Jan, which may be contributed to the thermal effects of this lake.