The invention relates to the technical field of image information safety and optical information processing, and aims at effectively resisting a known plaintext attack and selecting a plaintext attack and solving problems of secret key management and transmission from the aspect of secret key generation. The technical scheme of the invention is that a chaotic and Fresnel transformation and two-step generalized phase shift optical image encryption method comprises the following steps: 1), a secret key generation part: enabling an Henon chaotic system controlled by different chaotic parameters to generate two random phase masks playing a role of a main secret key; 2), an image encryption part: enabling a specific image to be modulated by the first chaotic random phase mask before encryption, carrying out the optical Fourier transform of the image, modulating the transformed image through the second chaotic random phase mask, and then carrying out the inverse Fourier transform of the image; 3), an image decryption part: obtaining a decrypted image. The method is mainly used in occasions of image information safety and light information processing.