A multi-image encryption scheme based on optical wavelet transform (OWT) and fractional Fourier transform (FrFT) is proposed, which enriches the multi-image encryption method. The scheme combines OWT and FrFT to make full use of multi-resolution decomposition of wavelet transform (WT). WT can focus most energy of the original images on the low-frequency parts, so the sizes of images can be reduced as far as possible without loss of image quality. The mentioned properties can not only realize the multi-image encryption, but also make sure each image is processed alone. When encryption is finished, each image will get its own independent keys. Analysis of encrypted effects is completed. Furthermore, the influence of WT type and order are analyzed, and application and analysis of independent keys are accomplished as well. Numerical simulation verifies the feasibility of the scheme and shows that the problem of insufficient capacity is solved better. The security of the method is analyzed. It can be concluded that the method expands the space of keys, which improves the security. Moreover, the application of independent keys makes the variability and flexibility of scheme increase, which means that multi-user decryption, cascade, and multi-user authentication can be achieved. A simple photoelectric mixed device to realize the scheme is proposed.