根据黄土高原绥德、延安、安塞和离石等地林、草地径流小区降雨侵蚀资料，对不同降雨和坡度下林、草地水土保持有效盖度进行了分析，建立了林地、草地水土保持临界有效益度与降雨及坡度的关系式。在土壤和植被类型相对稳定的条件下，林、草地的有效益度随着降雨和坡度的增大而增大，当临界有效益度达到一定程度时，降雨和坡度的影响减弱；在其它条件相同时，同一水土保持作用所要求的有效盖度草地比林地大。并结合降雨频率分析，得出了林、草措施抵抗不同年遇暴雨时的临界有效盖度。 Based on the data of rainfall erosion in the forest and grassland runoff plots of Suide, Yan’an, Ansai and Lishi on the Loess Plateau, the effective coverage of water and soil conservation for forests and grasslands under different rains and slopes was analyzed, and the thresholds of soil and water conservation for forestland and grassland were established Relationship between Effectiveness and Rainfall and Slope. Under the relatively stable soil and vegetation types, the effective benefit of forest and grassland increased with the increase of rainfall and slope. When the critical benefit reached a certain level, the effect of rainfall and slope decreased. Under other conditions The same time, the same soil and water conservation effect of the required coverage of grassland larger than the woodland. Combining with the analysis of rainfall frequency, the critical effective coverage of forest and grass measures against heavy rainfall in different years was obtained.