Different design methods for retaining structure of unsymmetrically loaded foundation pit in another foundation pit adjacent to railway are calculated and analyzed by finite element software; and the deformation rules of the retaining structure are analyzed based on monitoring data. The monitoring data show that: 1) For overloaded sidewall, the deformation of the sidewall increases with the excavation depth increases and moves towards inner foundation pit. 2) For underloaded sidewall, the deformation of upper part faces to outer foundation pit and that of lower part faces to inner foundation pit. The finite element analysis results show that: 1) The internal force of overloaded sidewall would be overestimated and the internal force of underloaded sidewall and the axial force of Support No. 1 would be underestimated when the slope excavation is ignored and the slope is equivalent to distributed load. 2) The internal force of retaining structure of underloaded sidewall would be overestimated when calculation is based on overloaded sidewall. 3) The integral characteristics of unsymmetrically loaded foundation pit in another foundation pit and the interaction between two foundation pits should be considered in design phase of the foundation pit.