Aiming at the problems of large cross-talk noise and small multiplexing capacity in the optical multi-image encryption system, an optical multi-image encryption method based on joint power spectral (JPS) partition multiplexing is proposed. First, the phase retrieval algorithm is utilized for the optimal design of phase masks and the single-channel JPS area is thus compressed. Then, the corresponding linear phases are superimposed on the optimized phase masks and so that the each-channel JPS is shifted differently in its spectral plane. After the window filtering operation, the superposition without crosstalk is realized. In addition, the key content planning is carried out in the form of “key phase kernel plus deflection angle packet”. While the security of encryption method and the large enough key space are ensured, the key data needed to be transferred is compressed. The numerical simulation results show that, when nine gray-scale images are encrypted, the correlation coefficients between the decrypted images and the original images are over 0.94 and the decryption effect is obvious. When the evaluation threshold of decryption quality is set as 0.95, the maximum compression efficiency factors of gray-scale and binary images reach 12 and 32, respectively. The cipher-text compression ability is remarkable. Finally, an optical experiment system is built and the feasibility of this method is further verified.