Abstract: A GIS-aided MIKE SHE model,distributed hydroloyic model,is used to simulate the stream flow in an ungauged Kaidu River Basin(19012 km²)with arid climate,which is one of the most important sources of Tarim River. Based on the GIS technique,the DEM of the study basin is successfuly used to delineate the stream network and to extract the information of catchments characteristics. Landsat TM data from 1995 to 2001 are utilized for various scale depended maps of the land use and vegetation,and leaf area index(LAI)from MODIS data is used as input data for the distributed hydrological modeling. Further,the root depths of the annual vegetation are related to the temporal and spatial variation of LAI. The observed discharge at Dashankou station is used for the calibration and validation. It is shown that a well-calibrated MIKE SHE model with five "free" parameters can produce the consistent results with the model efficiency coefficients greater than 0.7,the water balance error lower than 3%,and the simulated discharge is highly correlated to the observed discharge.