Abstract: The root distribution characteristics of two cuttage plants(five-year-old Salix alba var. tristis and Populus tomentosa)were measured by soil column method. The stability of water-stable aggregates and erodibility characteristics in different-layer soil under two cuttage plants were measured by rapid wetting treatment in Le Bissonnais method, and the measuring index included water-stable aggregates (>0.25 mm) content (R_0.25), mean weight diameter of aggregates (MWD) and factor of soil erodibility (K). Root distribution characteristics of two cuttage plants on the slope and their effects on soil aggregates were analyzed. The results showed that: 1) the roots of two cuttage plants mainly distributed in the 0-40 cm soil layer around the trunk, with >5 mm thick roots as the main components. 2) In the 0-100 cm soil layer, the root content, soil aggregate stability and soil erosion resistance decreased with the increase of soil depth. 3) In the aspect of increasing soil aggregate stability and erosion resistance through root system, Salix alba var. tristis was better than Populus tomentosa. 4) R_0.25 and < 1 mm root content showed a significantly positive correlation, indicating that the performance of roots in improving soil aggregate structure was mainly determined by < 1 mm root content.