According to the calculation of the water resources of the Shiyanhe,Heihe. Shuleke River basins in the Hexi Corridor and their original runoff volumes, it shows that the actual annual water resources in the oasis of every county and town of the Hexi Corildor are 285-770mm,which is 1. 3-18. 5 times the local annual precipitation. From the point of view of ecological balance, the ecological water need in oasis in every county and town is 400-500mm and that in the farmland is 450-650mm. On the basis of the above mentioned calculation,to basically keep the natural ecological balance of every county and town, the proper oasis area should be 2. 92- 17. 26 ×10⁴ ha,and that in the whole Hexi Corridor may be expanded to 117. 24 × 10⁴ ha ,which is 6. 61 × 10⁴ ha larger than now; the proper farmland area should be 1. 43- 8. 28 ×10⁴ ha and that in the whole Hexi Corridor may be expanded to 57.98 × 10⁴ ha,which is 9. 32 ×10⁴ ha larger than now.