Abstract: In this paper, Based on the weighted GS algorithm, as an example, a 16-phase level binary optical element designed for transforming the input Gaussian beam into nearly flat-top, The size of weight's influence to the binary optical element is numerically simulated, at the same time, we designed a 16-phase level binary optical element with the best weight, and compared with the results abstained by other weights, the simulation results show that with the increase of the weight, the averages square difference reduced, but the diffraction efficiency also reduced.