A new asymmetric optical image encryption algorithm based on anamorphic fractional Fourier transform(AFrFT) is proposed,which introduces the nonlinear phase-truncated strategy to get rid of the potential insecurity existing in the linear symmetric cryptosystem.The amplitude-phase encoding is employed to achieve single-channel multiple images encryption combining with the phase truncation operation,and five images are encrypted into one real-valued ciphertext by using a set of optoelectronic hybrid devices repeatedly.Four private keys are generated by phase reservation operation and determined by the original images,and the fractional orders of the AFrFT and the private keys can enhance the safety strength of the encryption algorithm.Numerical simulation results demonstrate the feasibility and effectiveness of the proposed method,and the security of all keys has been analyzed with the mean square error(MSE) between decrypted image and original image.