Based on the engineering example of Nanjing city gate of Wuding subway foundation pit, the paper uses the finite element analysis software PLAXIS to simulate the design parameters of underground continuous wall. The influences of the different factors on underground continuous wall were discussed. The support design method was optimized by according to the comparison results. The results show that increasing the stiffness of diaphragm wall can effectively reduce the lateral displacement of underground continuous wall; if the depth of underground continuous wall meet with the minimum depth, then increasing the depth is of little significance; the concrete support replace steel support, which could increase the support stiffness, reduce the horizontal spacing and adding a layer of support along the vertical direction when it is necessary, which has good effect on reducing the deformation of diaphragm wall; At the same time, the soil reinforcement to the weak soil around pit surrounding and structure risk areas has a very good effect to control the deformation of foundation.