Abstract: The spatio-temporal variation of annual runoff in the Jinghe River Basin of Northwest China and its main driving forces were studied based on the meteorological and hydrological data over 50 years in this paper. It showed that the precipitation and runoff presented an obvious decreasing trend from south to north in the Jinghe River Basin, the high value areas of both precipitation and runoff existed in the upstream mountainous parts. While the averaged temperature in the basin increased significantly in last 50 years since the 1960s, the pan evaporation decreased slightly and the precipitation decreased insignificantly, the annual runoff of the whole Jinghe Basin decreased significantly from 50.1 mm in the 1960s to 22.3 mm at the beginning of the 21^st century. However, the runoff reduction among subbasins differed significant, which manifested the highest runoff decrease in the west, southwest and southeast parts of Jinghe River Basin, with a reduction rate up to 17.5 mm/10a; while the runoff reduction in the north and northwest parts of Jinghe River Basin presented an unobvious runoff reduction, with a maximum reduction rate of 1.3 mm/10a. The change of annual precipitation is an important cause for the runoff reduction, but the change of soil surface characteristics due to human activities became more profound cause for the runoff reduction since the 1990s, including the increasing terrace field and forest/vegetation coverage resulted from a series of ecological restoration projects, such as grain for green and nature forest protection.