In order to study soil water infiltration under different revetment vegetation to provide references for regional riparian ecological restoration and water resources protection, three typical vegetation in the slope vegetation buffer zone of the Yongding River basin, including Willow, Vitex and Setaria were selected, dye morphology were studied by combining bright blue staining method with the software of Photoshop, Image Pro6.0. The development degree of priority flow was quantitatively evaluated based on fractal dimension and multi-index evaluation method, and the influences of different vegetation roots on priority flow was discussed. The results showed that water referential infiltration occurred in the soils under the three vegetation, the ratio of soil stained area (D_c) decreased gradually with the increase of soil depth, average D_c(38.32%) was the largest under Willow, which was 1.11 and 1.37 times of Vitex and Setaria, the length index and preferential flow fraction were significantly lower under Setaria than those of Willow (P<0.05), no significant difference was found in the depth of substrate flow under the three vegetation. The results of the priority flow evaluation index (P_FI) and fractal dimension (F_D) were consistent in the order of Willow > Vitex > Setaria, the wet front line fragmentation of Willow was the highest, and the priority flow phenomenon was the most obvious. Organic matter, non-capillary porosity and root length density significantly influenced water infiltration, the total root length density and non-capillary porosity were significantly positively correlated with D_c, F_D was significantly positively correlated with roots ≥1 mm and organic matter, and D_c was well fitted with root length density. In conclusion, under the same external conditions, Willow priority flow degree was greater, the diameter class and density of plant roots significantly influenced the development of preferential flow, and the more abundant roots ≥1 mm, the more obvious the preferential flow phenomenon was, while the roots with diameter class <1 mm mainly promoted the uniform infiltration of surface soil water.