Abstract: In order to control the light propagation with high diffraction efficiency in 3-D space, a new phase weighted iterative optimum algorithm based on GS iterative algorithm is proposed to improve 3-D phase-only diffractive optical element (DOE) design. A weighted iterative algorithm model based on multi-diffractive output planes was established. In this algorithm, a dynamic phase weighted adjustment strategy based on the feedback of design error on each output plane is performed to optimize the conventional algorithm. A designing experiment was carried out to validate the effect of this algorithm. In this designing experiment, a phase-only diffractive element was designed to transfer the incident Gauss beam into 2×2 beam arrays in every plane, which occurred at 300mm ～ 400mm to the incident plane. It is found that this method can improve the convergent effect of the algorithm on the basis of the previous algorithm and achieve the better design quality.