Abstract : Research purposes ： In large and medium - sized cities， the municijDal engineering constructions have developed rapidly， which leads that the deep foundation pit engineering is more and more. Because of the lack of construction land，it，s evitable that there will be existing building or structures around the deep excavations. In this paper，combined with the rare condition that there are high - speed railway bridge pile - foundations around the deep foundation pit， through FEM numerical simulation， the influence pattern of deep foundation pit’ s excavation to supporting structures and pile foundations is analyzed， and then the numerical results are verified with on - site monitoring data. Finally，the conclusions can provide reference and guide for similar adjacent engineering. Research conclusions ：( 1) Deep foundation pit ’ s excavation causes the unloading effect，which breaks the balance of surrounding rock and soil mass， then stress redistribution occurs. (2) The deep foundation pit excavation causes the upheaval of foundation pit，and the envelop enclosure moves forward into the pit. (3 ) The stress field ’ s change causes the displacement field ’ s change，and the structure such as pile foundations in the rock and soil mass moves as the result of rock and soil’ s displacement. The direction of pile foundations is basically toward pit，whose displacement of upper part is bigger and displacement of lower part is smaller. (4) The simulation data is matched with test data，which means that the final displacements are all within the safety range，and proves that the supporting structure design in this project is effective to deep foundation pit ’ s safety. The kind of supporting structure design and pile foundations displacement patterns can be used in future similar engineering：