Monthly meteorological data were obtained from typical weather stations located in the upper Heihe River．The influences of climatic factors on the runoff of the river from the mountain areas in the last 50 years were investigated using correlation，multivariate regression，analysis of variance，and trend analysis． The results of correlation show that winter and summer precipitation，summer and autumn mean lowest air temperature had close correlation with the runoff volume． Based on the close relationship，multivariate regression models were then developed to simulate the temporal variations of the runoff from the mountain areas． However，summer mean lowest air temperature showed little contribution to the runoff based on the regression analysis． The annual variations of the runoff were controlled by the precipitation amount in summer． Trend analysis results further confirmed that the runoff varied consistently corresponding to the summer precipitation over time scales of decades．