The work aims to put forward the image encryption algorithm based on double beam coherent superposition and differential mode vector decomposition, in order to solve the problem of low security induced by silhouette existing in current optical image encryption algorithm based on the principle of interferometry. Firstly, the plaintext was transformed into complex function in Gyrator domain based on Gyrator transform. Then, upon the introduction of vector decomposition method, the complex function in Gyrator domain was differentially decomposed into two vector components with unequal output amplitude and phase. The vector components were modulated by two phase masks for taking it from the frequency domain to the spatial domain, of which the phase part was regarded as private, and the amplitude part was regarded as the final encrypted cipher. The experimental results showed that, compared with the current image encryption technology based on the equal mode decomposition, the proposed algorithm had higher security and sensitivity that effectively eliminated the silhouette problem. The proposed algorithm can ensure the secure transmission of image information in the network, and effectively resist external attacks. It has certain application value in the field of packaging, printing and anti-counterfeiting QR code.