As the resolution of the interferometer is rapidly. increasing, the higher requirement is proposed fo the interferometry. For avoiding losing of the useful information of the actual interferogram, an algorithm is presented based on singular value decomposition (SVD). which is more stable than other algorithms to some extent. The weight . coefficients of the orthogonal polynomials can be worked out directly, which can eliminate.the}computational error. Then an evaluation criterion is developed to choose the optimum Zernike polynomial number. The computer simulations of this algorithm are also made. The simulation experiments have proved that it is an efficient algorithm and can reconstruct the wavefront accurately ami stably.