Abstract: Based on the observations on precipitation,ice and snow melt,evaporation and runoff in the mountainous basin of the rmqi River,which is located at the north flank of the middle Chinese Tianshan Mountains,the runoff formation processes are discussed in this paper.A systmatic underestimation is found in the precipitation measurements by the Chinese standard gauges.The annual correction factor required is 31% for the high mountain zone,14% for the middle mountains and 26% for the front of the mountains. The solid precipitation increases with altitude in the mountains,and even is summer,solid precipitation is dominant at the high mountain zone.Both summer and annual precipitation increases with altitude,and thus the precipitation in the mountainous basins is abundant compared to that in the low land in front of the mountains.The meltwater is calculated using the parameterized heat flux expressions based on the standard meteorological elements.The measurement and calculation of the evaporation from the apline meadow indicate that the weighing lysimeter and Bowen ratio methods are more accurate than the profile flux method.The yearly variation of evaporation in the mountainous basins is small,but the monthly variation is large.The maximum monthly evaporation occurs during June and July,accounting for 37% of the annual evaporation,while the evaporation from May to September accounts for 75% or more of the annual value.The precipitation,evaporation and runoff coefficients of the mountainous basins are much larger than the mean values of those in the inland river area of China.The water storage change of the mountainous basins are mostly attributed to the glacial storage change.Along with the increase of the mean altitude of the mountainous basins,the runoff and runoff coefficient also increase.