Abstract: The cantilever retaining structure is more sensitive to the deformation than the internal bracing retaining structure. The excavation of pit-in-pit will bring great impact on the cantilever retaining structure. By using the finite element program to establish pit-in-pit models and to perform comprehensive numerical simulation studies, the deformation characteristics of the outer pit are studied in the cases of different positions, depths and areas of the inner pit excavation. Moreover, the measures to control the deformation are also discussed. The results show that the maximum lateral deformation on cantilever retaining structure increases with the decrease of pit toe coefficient which has a critical value. However, they perform completely opposite in terms of depth ratio and area ratio. The depth ratio has the greatest impact on the lateral deformation of cantilever retaining structure, while the area ratio has the least impact on it. The increase of the stiffness and embedded depth of cantilever retaining structure has no significant effect in inhibiting the increase of the deformation of the retaining structure of the outer pit. However, it performs completely opposite if the inner pit has internal bracing.