The present invention discloses a method and system for symmetrical and asymmetrical encryption and decryption of images. A first public key, a second public key, a first secret key, a second secret key and a third secret key are employed to perform encryption of an original image, and the image is compressed in the encryption process; and a first private key, a second private key, a first secret key, a second secret key and a third secret key are employed to perform decryption of the encrypted image, and the image is decompressed in the decryption process. The symmetrical encryption and the asymmetric encryption are combined so as to improve the safety and reliability of the encryption. In the image encryption process, the image is compressed to reduce the information content so as to facilitate storage and transmission of a lot of data. The method and the system can perform safe and reliable transmission for a lot of data.