【英文摘要】In this project, the key problem is to estimate groundwater renewal rate. Based on the water cycling theory and isotopic hydrology, many environmental tracers(D, O-18 and 3H)and water chemical information in unsaturated zone and aquifers were used to study groundwater flowing mechanism in Zhangye basin, northwestern China. And then two isotopic (tritium) models were coupled with a water flowing parameter to estimate groundwater renewal rate. The results suggested that: ① there existed rainfall infiltration in Zhangye basin where the water table buried depth was more than five meter-at sand dunes area, rainfall infiltrating coefficient is of 0.10～0.11 with water table buried depth being of 6.3m, while at the wasteland area, rainfall infiltrating coefficient is about 0.13～0.14 with water table buried depth being of 8.6m; ② the groundwater flowing system can be treated as a combined exponential-piston flow mode and the water flowing parameter, that was used in groundwater tritium age model, can be regarded as the parameter of the coupling model. This parameter values change with spatial dimension. In piedmont plain, the parameter value is of 9～11, while in the floodplain, the parameter value is of 4～6; ③ the groundwater renewal rate, that was affected mainly by recharge conditions, changed from 2.5%/a in the piedmont plain to 0.5%/a in the floodplain. Groundwater renewability was also affected by geological structure. Except for existing some buried faults, the piedmont area of Minle has the same hydrogeology conditions with the piedmont area of Zhangye, but the real groundwater flow velocity is of 0.7m/d, that is about 1/3 of that in the piedmont area of Zhangye. This study would not only provide the basic parameters for groundwater resource development and groundwater protection in Zhangye basin but also provide the referenced method for estimating groundwater renewal rate in arid area.