Soil reinforcement is often used to reduce the lateral deformation of retaining structure in foundation pit projects. In order to study the influence of pit-in-pit soil reinforcement on cantilever retaining structure, we established an elasticity-plasticity calculation model for soil reinforcement of pit-in-pit by using ABAQUS and discussed the effects of depth, width, stiffness, location and size of reinforcement body on retaining structures of inner pit and outer pit. Calculated results show that 1) there is an optimum interval for the values of depth, width, and stiffness of passive reinforcement zone respectively, beyond which the reinforcement effect on retaining structure of pit will be not obvious;2)for pit-in-pit, the effect of stepped reinforcement in the passive zone of outer pit could reach that of full-size soil reinforcement, hence is more economic;3)when reinforcement width and reinforcement depth of each step are approximately equal, the reinforcement effect is good. Finally, the research results can be taken as reference for pit-in-pit retaining structure in actual projects.