Based on precipitation observational data at the weather stations in the mountain drainage basin of the Heihe River and historical material and tree growth ring record in the recent 50 years, the variation characteristics, possible causes and trends on the multi-yearly mean precipitation in the region are analyzed.The results show the response of the precipitation in the region to global climate warming is obvious, so the precipitation in the region presents a little increasing trend.Because the subtropical high of west Pacific is closly related to the global air temperature change, and the strengthening and expanding of subtropical high of west Pacific is of advantage for East Asian summer monoon moving forward to north or even more, which will bring on the increase of precipitation in the mid-and-west parts of the Qilian mountain.Therefore, as a whole, the global climate warming is favourable for the increase of precipitation in the mountain drainage basin of Heihe river.The climate of the mountain drainage basin of the Heihe River is just in the fifth warm periods or the third warm-humid periods in the histrial data records at present and it began from 1980's.We forecast that the precipitation in the mountain drainage basin of Heihe river with the further warming of the global climate will continously maintain the slow increase in the future some years.