Aiming at the low diffraction efficiency of optical beam splitting devices, based on the traditional Gerchberg-Saxton (GS) algorithm, the initial phase and the amplitude limitation method is improved. The secondary phase is used as the initial phase of the iterative algorithm, and then the output plane is divided into the signal area and the noise area. Keeping the phase of the two parts unchanged, the amplitude in the region is multiplied by a factor which varies with the number of iterations, and the amplitude in the noise region remains unchanged. A 9×9 continuous-face beam splitting device designed by the proposed method is compared with the beam splitter designed by the traditional GS algorithm. The results show that the phase of the beam splitter designed by GS algorithm has serious mutation and discontinuity. However, the beam splitter phase designed by the proposed method is continuously smooth and can be processed by the moving mask technique.The 1×3 and 1×9 beam splitters are prepared, the measured diffraction efficiency are 83.5% and 89.4%, the uniformity error are 3.56% and 15.23%, respectively.