In order to explore the reinforcement mechanism of fiber to soil, a direct shear test was carried out by discrete element method to analyze the particle movement characteristics of texsol and plain soil in the shear process. A plain soil model and a texsol model with 0.6% fiber content were established. Besides, three typical displacement points were selected to analyze the movement characteristics of plain soil and texsol at the typical displacement points. Conclusions are as follows. The texsol has a larger displacement at the shear part and a smaller displacement at the upper part, showing greater integrity. Before the peak displacement, the large corner area of texsol is larger than that of plain soil. After the peak displacement, the large corner area of the plain soil is coarse, and there is basically no large corner area in the surrounding soil; the large corner area of the texsol is thin, and the large corner area is in the surrounding soil, distribured in strips. The large turning angle of texsol is mainly distributed at the shear and fiber. The shear zone of plain soil is larger than that of texsol. The relative sliding and relative rotation of the texsol in the shear zone are slightly larger than that of the plain soil. The relative sliding and relative rotation of the texsol and plain soil outside the shear zone are not much different. Both the relative sliding and the relative rotation of the soil inside and outside the shear zone increase with the development of shear.