To investigate the impacts of typical herbaceous plants roots on soil resistance to runoff erosion in the reservoir riparian zone, simulation flume experiments of undisturbed-soil were carried out to study the soil erosion resistance of 0-20 cm soil layers of three grasslands (Cynodon dactylon, Hemarthria compressa and Xanthium sibiricum), and the bare land was taken as CK, and the root characteristics of different herbaceous plants and their effects on soil erosion resistance were also discussed. The results indicated that:(1) The roots of the three herbaceous plants mainly distributed in 0-10 cm soil layer, root weight density, root length density, root surface area density and root volume density of H. compressa were significantly higher than those of C. dactylon and X. sibiricum (P<0.05). (2) With the prolonging of scouring time, the runoff sediment concentration of all soil samples decreased sharply at first and then gradually stabilized. The sediment concentration was higher and decreased rapidly within 0~3 min after discharge, decreased slowly within 3~6 min and stabilized within 6~10 min. Compared with the CK, the runoff sediment content could be effectively reduced in the different grasslands in the 10-minute scouring process. The runoff sediment concentration of 0-10 cm soil layer followed the order of CK > C. dactylon > X. sibiricum > H. compressa, while that of 10-20 cm soil layer followed the order of CK > C. dactylon > H. compressa > X. sibiricum. (3) During the scouring process, the index of soil anti-scourability increased slowly at first and then increased rapidly, it was small and increased slowly within 0~3 min, gradually increased within 3~6 min and rapidly increased within 6~10 min. Compared with the CK, the root systems of different herbaceous plants could effectively increase the soil anti-scourindex, while there was a significantly difference between the three grasslands and the CK in 0-10 cm soil layer. The index of soil anti-scourability of H. compressa grassland was the largest, which was 2.15 times of the CK, followed by X. sibiricum and C. dactylon grasslands, which were 1.60 times and 1.43 times of the CK, respectively. Furthermore, there also was a significantly difference in the index of soil anti-scourability between the grasslands and the CK in 10-20 cm soil layer besides the C. dactylon grassland. (4) The enhancement effects of herbaceous roots on soil anti-scourability mainly occurred in 0-10 cm soil layer, and the enhancement effects of H. compressa roots on soil anti-scourability was the largest, followed by X. sibiricum and C. dactylon. The soil anti-scourability was closely related to root distribution and morphological indexes, especially root surface area density and root volume density of roots with diameter (D) ≤ 1.5 mm.