Because the kinoform has good diffraction efficiency,it is often u sed in computer-generated holograms.When calculating the kinoform,a random phase is added to the object to diffuse the object light in the hologram.However,the addition of random pha se will cause considerable speckle noise in the reconstructed image.In order to improve this problem,in t his paper,we first analyze the range of random phase,study the influence of initial random phase on the im aging quality of hologram,and then find the optimal random phase range by particle swarm optimiz ation.There is some loss of information when calculating the hologram,so the iterative operation of the hologram can make up for the difference between the holograms.Therefore,this paper will also com bine the improved iterative Fourier transform algorithm to effectively improve the quality of reco nstructed images,and a method based on particle swarm optimization for analyzing the influence of finite rando m phase on hologram quality is proposed.Through numerical simulation and optical experiments on the above process,the results show that the high-quality reconstructed image can be improved by finding the optimal random phase range and using the improved iterative Fourier transform al gorithm to reduce the speckle noise of the reconstructed image.