Based on daily runoff data of Hutubi River Shimen station,the smoothed minimum method and recursive digital filter were used for base flow separation,the recursive digital filter and smoothed minimum method were used for base flow separation.Annual and interannual variations in baseflow,baseflow index(BFI),and the variations in BFI for different water level years in Hutubi River basin as well as the main controlling factors(temperature and precipitation)were investigated in different time scales.It is found that the smoothed minimum method is more suitable than recursive digital filter in the study area.Annual distribution of baseflow is in unimodal type,with the maximum value appearing in July,the BFI distribution in ayear,with the minimumBFI value in May.BFI is close to 1in dry year.The average annual base flow is 3.67*10~8 m~3.The base flow is increasing in the Hutubi river.The base flow index is 0.78in the study area, it is in slowly decreasing trend.Averaged BFI from the smoothed minimum method in dry years,average years,and wet years were 0.78,0.76 and 0.74,respectively.Temperature and precipitation are two important factors,and their importance to baseflow varies with seasons in different water level years.The results implied that the effect of temperature on baseflow was higher than that of precipitation in spring and autumn. Temperature plays a leading role in the effects on baseflow in spring and autumn,and temperature is a key affecting factor on baseflow of Hutubi River.