Abstract: A simple method is introduced to reconstruct the nearfield wave-front from intensity distribution near foal plane, which is treated in this paper as an optimization problem. Proper orthogonal decomposition technique is applied to describe the wave-front to be reconstructed. By optimizing the coefficients of the polynomial to minimize the differences between simulated intensity distributions and the real intensity distributions, nearfield wave-front can be reconstructed and characterized. Simulations are carried out upon square-aperture beam using Legendre polynomial. Conjugate gradient method is used and optimization is performed for several steps to reduce executing time. The results show that the reconstructed wave-front are consistent well with the reference wave-front.