In order to acquire the stress and deformation performance of retaining structures and to ensure the construction safety of deep foundation pit with irregular crosssection, numerical simulation calculation is made by means of finite element software ANSYS and the calculation results of each construction step are analyzed, with No. 1 transfer hall of No. 3 bid section on No. 6 line of Beijing Metro as an example. Conclusions drawn are as follows: 1) The pile length and the rigidity of the connection to Type B piles should be increased, so as to increase the stability of the retaining structure. 2) The frame structure formed by the floors has obvious constraining effects, which is helpful to the control of the deformation of the retaining structure. 3) The weak points of the irregular foundation pits should be considered in the arranging of the internal supporting system of the foundation pit. The stability of the platform can be guaranteed by rapidly installing the connection between neighboring piles and increasing the rigidity and prestress of the steel support below the platform.