Using Abbe^,s imaging principle and symmetric-asymmetric hybrid encryption scheme, the optical image encryption and decryption based on 4f optical system are realized. First, the Lees detour phase encoding method is used to make the phase mask corresponding to the encryption function as the key, and the frequency domain encryption of optical image is completed by spatial filtering method. Secondly, the computer decryption is realized with the program developed by the authors, which gets rid of the difficulty of precise alignment of phase mask during optical image decryption, and greatly improves the efficiency and quality of decryption. Finally, the experiment reveals that the encryption method has high security level, and it also proves this experimental method possesses good robustness under mild noise influence.