In order to improve the efficiency of transmission and security of the optical encryption system, a multiple binary images optical encryption technology is proposed. This technology uses digital method and optical method in the encryption process, and pure optical method in the decryption process. In the encryption process, each original image’s spectrum is spread by multiplying with a encryption key and then all the images are added together to generate a composite image. The composite image is put on the input plane of the joint transform correlator for optical encryption. In the decryption process, each of the original images needs to be extracted from the composite image by an aperture in the frequency domain. Through theoretical analysis and computer simulation, the multiple binary images optical encryption technology system is very simple, and it has high image multiplexing capacity and security.