Abstract: A new bit-level image encryption algorithm based on chaos is presented with the properties of chaotic sequences and inherent characters of bit-level images.At first,the plain image is divided into 8 bit-level images which are treated as a group.And the bit-level images'group is permutated using chaotic sequences generated by Chen's chaotic map.Then the image pixel-level diffusion is carried on using Logistic chaotic sequences.Finally, experiments have been carried out to compare its performance with that of other schemes,and the results justify the superior security of our proposed algorithm.