Current hologram computation suffers from low efficiency and loss of encoded information. To address these issues, a novel encoding method for complex amplitude hologram is proposed. The proposed approach decomposes the complex amplitude distribution calculated by the angular spectrum method into amplitude and phase information, then generates a hologram containing complete amplitude and phase information through multi-phase encoding. Compared with the traditional Gerchberg-Saxton （GS） algorithm, under the same computation time, the proposed multi-phase encoding method improves the PSNR of the reconstructed holographic image by 15.49 dB and the SSIM by 0.65. This method provides a new approach for enhancing the quality of holographic reconstructed images for three-dimensional display.