The traditional least squares method(LSM) is improved by introducing the second derivative of the detected wave-front. Both the shearing data along one direction and two orthogonal directions are analysed using the improved LSM. And the spatial distribution of the wave-front recovered by the proposed method is compared with that of recovered by the gridding method and the integration method. The frequency response and the aperture spatial distribution characters of the wavefront recovery of lateral shearing interferometer are also analysed respectively to the annualar aperture and the combined one using the two orthogonal latering shearing data. The simulation results show the wave-front confined by any aperture could be recovered from two orthogonal lateral shearing data using the proposed algorithm.