In order to suppress the speckle noise on holographic display, we present one method for introducing initial phase to desired objects when generating computer hologram. The method considers the relationship of gray value among the adjacent pixels. We perform simulation in order to verify the effect of proposed method. We compare the proposed and traditional methods and conclude that proposed method is better than traditional methods in terms of the quality of reconstructed image. We believe this method can greatly enhance the quality of reconstructed images and it will be widely applied in the holographic field in the future.