To explore the difference in shear strength of different plant root-soil composites and the influence of various factors on it, four different vegetation coverage areas including coniferous forest, broad-leaved forest, shrub, and grassland in Wenchuan County were selected as the study area. Sixteen dominant plant root-soil composites and unrooted bare soil original samples were prepared in the field, and indoor fast shear experiments were conducted. The enhancement effect of the typical plant roots on the shear strength and deformation resistance of the soil were analyzed. The gray correlation method was used to analyze the degree of influence of the roots and soil related factors on the shear strength of the root-soil composite. The results showed that: (1) The addition of 16 kinds of plant roots could improve the shear strength and deformation resistance of the soil to a certain extent, and the shear strength was mainly enhanced by increasing the cohesion of the soil. The cohesion of the root-soil composite was greater than that of the bare soil by 6.09%~153.27%. Different root systems had obvious differences in enhancing the cohesion of the soil. But the internal friction angle did not change significantly, and most of them were slightly smaller than that of the bare soil. (2) The gray correlation degree of each factor with cohesion and internal friction angle was relatively large, among them, the correlation degree between cohesion and dry density was the highest (0.803), followed by root weight density (0.793), and plasticity index was the lowest (0.626). The correlation between internal friction angle and plasticity index and dry density was relatively high (0.789, 0.700), D_c was the lowest (0.567), and the influence of root characteristic parameters on internal friction angle was not significant.