The benefit of a test reformed low beneficial protection forest established on the Huaying mountain has been observed and appraised. The result shows that the hydrologic benefit of reformed low beneficial protection forest is obvious. Having been implemented reformation for five years, the available soil water for various re formative way has increased by 14. 0%～38. 0% over the unstocked forest land. In the portioning of annual precipitation,the storage of soil water was 55. 5%, the surface runoff was merely 1. 8%, the permeant runoff was 8. 7% and the runoff in soil was 23. 7%,the annual runoff coefficient in whole woods was 0. 341 5,it has decreased by 12. 48% under the annual average runoff coefficient determined by Beibei Hydrology Station. The runoff coefficient in the plentiful water period has reduced by 22. 52% as compared with Beibei Station,but in non-plentiful water period,it has heightened by 20. 35%. Therefore,reforming low beneficial protection forest has a very high benefit of storing water,decreasing flood and regulating discharge in rivers.