The paper based on a foundation pit with pile-strut-anchor supporting structure in order to analyze the deformation of the pit. With the aid of finite element method the curves of relationship between horizontal displacement of pile body and depth, the relationship between horizontal displacement of soil adjacent to excavation and time were obtained. And then the law of change was summed. The maximal displacement appeared on upper part of the pile or turned up on the top but incremental displacement became small. The deformation of soil adjacent to excavation was directly related to the stage of excavation and had the characteristics of phase change. Through comparative analysis the result of finite element method simulation was in conformity with monitoring results. Therefore we can claim that this calculating model is appropriate and supporting structure is safe.