A new algorithm for digital image scrambling and encryption based on magic cube transformation is proposed. It is different from the general algorithm which implements image scrambling and encryption by rearranging the position of image pixels without changing the value of the pixels. The algorithm performs the image encryption in three-dimensional space and changes all the features of original image. A code rule of correspondence mapping from secret key to magic cube transformation is proposed,Which can realize that the secret key is not limited by both type and size,and the key space is huge. The result of simulation shows that the algorithm can give satisfactory result of encryption and decryption.