Based on the foundation pit engineering case of the pit-in-pit of Nanchang Aixihu tunnel，the deformation characteristics in different spatial forms of the pit are studied and analyzed by using the numerical calculation software. The influence rate of foundation pit deformation is proposed, which can be used to comprehensively judge the sensitivity of pit spatial shape parameters to foundation pit deformation. The results show that the influence factors of the spatial form characteristics of the deformation characteristics of the pit in pit are mainly the relative size, relative position of the inner and outer pits and the insertion ratio of the enclosure structure. The specific sensitivity relationship is as follows: relative depth ＞ relative position ＞ insertion ratio of the outer pit enclosure structure ＞ insertion ratio of the inner pit enclosure structure ＞ relative width.