Short anti-sliding pile is widely used as the common treatment measures to landslide， however， its bearing mechanism is not clear. In this paper， the software of Fast Lagrangian Analysis of Continua in 3 Dimension （FLAC^3D） is used to build numerical model of anti-sliding piles to reinforce landslides with different length， the characteristics of deformation of the landslide model and the mechanics of the anti-sliding piles are analyzed， and the mechanics to reinforce the landslide is further revealed. The results show that： （1）the stability of the slope can be increased obviously with the reinforcement by short anti-sliding pile with different length； （2） with the increase of the short pile length，the stress of the pile spreads more evenly， and the integrity of the pile and soil is better， the maximum displacement of slope is reducing with lower reduce rate； （3）The slope destroyed cross over the pile when the ratio of the pile’s free section length to the thickness of the landslide is less than 0.6； （4）the ratio of the pile’s free section length to the thickness of the landslide is suggested to be 0.7~0.9.