Abstract: The spatiotemporal distribution of precipitation was researched based on the monthly precipitation data form 99 meteorological stations in the east of northwest China. The results revealed that the precipitation in the study area was slightly decreased, especially in autumn, and there was no significant sharp change of annual precipitation. Precipitation in autumn was in an increase trend in recent decade. Precipitation in the east of northwest China occurred mainly in the southof Ningxia and the east of Qinghai. There were the 4, 8 and 12year periodicities of precipitation. EOF was used to analyze the annual precipitation, the first mode was identical in all the regions, the second one was different between the north and the south, and the third one was different between the west and the east. Based on the ground conditions, it was found that the landforms, especially the plateaus, Liupanshan Mountain, deserts and Gobi deserts (including the Badain Juran Desert, Tengger Desert and Mu Us Sand Land), were the important factors affecting precipitation in the east of northwest China.

Key words: precipitation, spatiotemporal distribution, periodicity, EOF, landform, the east of northwest China