///After Wenchuan earthquake Ms 8.0 occurred at 14:28:01. 42 CST on 12 May 2008, all regions except Xinjiang, Jilin and Heilongjiang in China were affected by the great quake. It is a remarkable problem that how strong the coming earthquake in the Hexi seismic belt may be in the future time. In this paper, the authors have measured strontium and helium isotopic compositions of groundwater in Zhangye, Wuwei and Jiuquan Basins. It is concluded that the groundwater in these three basins are not originated from the runoff of Heihe River, Shiyanghe River or Shulehe River respectively, but from the supply of rainfall in the Qilianshan mountain front, which feeds the deep fault zones and then flows up over the Earth surface. The groundwaters in different areas have different cycling routes. Therefore, the fault zones within the Hexi Basin are strongly active at present.
