In practical engineering, rock mass in the long and narrow deep foundation pit of subway station is usually excavated in partitions. To obtain the stability rules of deep foundation pit excavated in partitions, finite difference software was adopted for numerical simulation. The deep foundation pit of a subway station in Hefei was taken as a case study. Through comparison between model results and field measurement results, the variation rules of retaining structure’s lateral displacement and lateral support axial force and ground surface settlement during partition excavation were obtained. Results show that 1)field measurement results are in agreement with numerical simulation results, both within standard limits, indicating that the numerical model could well reflect the deformation characteristics of the foundation pit; 2) with the proceeding of excavation, the “belly” of retaining structure bulged apparently, with the maximum displacement point moving towards the middle of the foundation pit; 3) axial force of support developed rapidly in the early stage, and then tended to be stable; 4) the adjacent ground surface settlement was in a groove shape, and the range within 40 m was affected by foundation pit excavation. The results could be taken as reference for the design and construction of similar projects.