A kind of angular-multiplexing optical image encryption scheme is proposed based on Fresnel-transform holography and random amplitude encoding. By introducing reference plane waves with different incident angles in the output plane, we accomplished multiple-image encryption. To enhance the feasibility of the system and decrease the coding complexity and precision requirement for random-phase mask, random-amplitude masks were positioned in the input plane and inserted into the reference arm, and some digital manipulations were applied in the encryption and decryption procedure. We analyzed the encryption and decryption quality of the proposed encryption method together with the influence of different random number generators. Numerical simulation proved the validity of the proposed scheme.