We propose a kinoform-based iterative random phase encryption method, in which t he phase retrieval algorithm is divided into two steps: 1) random phase encrypti on and 2) iteration solving for phase distributions of both the key phase plate and the kinoform. Since the iterations are executed between a Fourier spectrum a nd the kinoform, the decryption errors can be effectively depressed. By the quan tization process for the phase distributions during the iterations, a method of increasing the abundance of design is used to depress the decryption errors. The simulation results are presented at the end, which agree well with the theoreti cal analysis.