To investigate the stress and deformation evolution of the deep foundation pit pile-anchor support system in hard rock formations, relying on the support project of Laoshan public health center foundation pit, real-time monitoring was conducted on the prestressed anchor bolt axial force, horizontal and vertical displacements of the completed area of the south side support. The mechanical performance of the pile-anchor support system under these geological conditions was analyzed, and the factors influencing the rapid decrease of anchor bolt axial force and the increase of horizontal displacement of the foundation pit were discussed. The results show that the continuous and rapid decrease of the axial force of the prestressing anchor cable is related to the earth pressure of the foundation pit adjacent to the original mountain and the continuous construction of the back excavation area on the north side, and the project takes 2 times of compensatory tensioning of the prestressing anchor cable to apply good effect. The maximum horizontal displacement of the foundation pit is 19.98 mm and the maximum vertical displacement is 12.11 mm. The deformation of the foundation pit support system in the completed area of the south side support is obviously influenced by the subsequent construction area. The pile-anchor support system has good applicability and reliability in ultra-deep foundation pits in hard rock and soil-rock binary strata. The design of support structure of similar projects should pay attention to the influence of surrounding geological environment and continuous construction in neighboring areas.