A new image encryption technology based on computer generated hologram (CGH) combined with the 4f system of double random phase image encryption technology is proposed. The unique spread spectrum characteristics of CGH recording encryption image is analyzed, achieving the computer simulation of using the original of phase plate, conjugate panels and the combination with them as the decryption keys of the different spectrum units or spectrum units combination. And the anti-noise ability of this image encryption method is also analyzed. This proposed method improves the security of image encryption.