This paper divides the wall deformation into two parts, the parabolic flexible part and the trapezoidal rigid part. By solving the two-dimensional partial differential equations of plane strain, the basic solution of parabolic boundary problem is obtained. The settlement curves are given to show the characteristic of ground settlement. The theoretical solution is used to analyze the problem in practical engineering. The applicability of this theoretical solution is analyzed by qualitative comparing with the normalized settlement curves of four foundation pit excavation cases. The parabolic deformation of wall will cause concave-type settlement profile, in which maximum surface settlement occurs at a distance away from the wall back. The theoretical prediction indicates that the ground settlement is independent of the soil elastic properties; and the location of largest surface settlement is close to the measured data, as well as the pattern of soil settlement, which indicates that the theoretical solution is reasonable.