Foundation pit excavation will cause settlement and displacement of surrounding existing buildings and roads. In order to study the influence law of soil unloading on the surrounding buildings during pit foundation excavation, the application of pile-anchor retaining structure in deep foundation pit was studied by taking the deep foundation pit project of Anhui Bright Pearl Mall as the research object. Through theoretical analysis, field measurement and Fast Lagrangian Analysis of Continua 3D (FLAC3D) numerical simulation, the supporting structure is comprehensively analyzed, and the deviation between the measured displacement data and numerical simulation results of the supporting structure and surrounding environment during the excavation process of the foundation pit is compared. The results show that: the model results are generally similar to the field measured data by using the software of FLAC3D to perform numerical simulation, which can more accurately reflect the evolution law of soil pressure and deformation in foundation pit excavation. The maximum displacement of the horizontal displacement monitoring point of the foundation pit of this project is 25.96mm, which is less than the monitoring alarm value of 30mm. the horizontal displacement monitoring of the sidewall of the foundation pit is the key point among them. The three major causes of numerical deviation are analyzed, which has certain reference value for the design of deep foundation pit supporting structure.