Analysis of convex location and concave location as the central section of composite soil nailing wall was normally overcautious or unsafe due to the typical spatial effect at convex and concave locations. Behaviors of deformations at convex and concave locations were analysed accordingly by three-dimensional elastoplastic FEM. The results show that the most dangerous area with maximum deformation is the side near convex location of foundation pit; and deformation of concave location is less than convex location evidently.