This paper studies the deformation of deep excavation in mountainous area of Guizhou. The finite element method and large finite element method program ANSYS10.0 are used to simulate and analyze excavation and adjacent buildings interaction. In this model, the study issue has been presumed as plane strain. Seemly, the soil is seemed as ideal elastoplastic model, and four-node equal-parameter element is used abiding by Drucker-Prager yield criteria of soil. At the same time, contact element is set between pile and soil to simulate the interaction. What is more, this paper has analyzed the effect of bracing pile deformation by excavating with different distances between excavation and adjacent buildings, the different stiffness of bracing system and physical mechanics parameter variation of soil at the pile bottom.