Abstract: In order to gain a deeper understanding of the stress and deformation characteristics of existing building pile foundations on foundation pit pile anchor support structures and summarize the rules, a mutual demonstration method of engineering measurement and numerical analysis was adopted. Combined with a construction foundation pit project in Changsha County, a model was established using midas GTS software. From the length of building pile foundations, the distance between building pile foundations and the edge of the foundation pit consider the influence of three factors on the mechanical characteristics of pile anchor support structures based on the load of building pile foundations. Research has shown that when the pile length is less than the excavation depth of the foundation pit, the displacement and settlement values of the support pile body significantly increase with the decrease of pile length. The farther the distance between the building pile foundation and the edge of the foundation pit, the smaller the horizontal displacement, surface settlement, and pile bending moment of the support pile. An increase in the load on building pile foundations will cause an increase in the horizontal displacement and bending moment of the supporting pile body, and the growth rate is linear within a certain range.