A novel encryption based on iterative double random phase encoding and pixel scrambling technology is proposed. The principle of pixel scrambling method is described, and good results are given by numerical simulation used the proposed method. It is shown from numerical simulation that the original image can been reconstructed only when part of the encrypted image is used by this method. The relationship curves of the energy, noise and SNR of the decoded image via the pixels number of the decrypting image is given. By comparing the proposed method with the double random phase encryption, it comes to the conclusions that this method has better performance than the double random phase encryption, and the SNR of the decoded image will not decrease due to pixel scrambling. Finally an optical approach to realize the pixel scrambling is also proposed.