Abstract: Two phase mask plate with independent chirp signals are used to encode image in the joint transform correlator,so as to make encrypt the original image.The characteristic of this method is when decoding,the rotation of encrypted image can not affected decoding effect,and moreover,owing to the fact that phase distribution is a decisive function only grasped by owner of secure key and the secure key can be regenerated.It makes the practical use convenient.The results of computer simulation shows the feasibility of this method.