Abstract: In order to effectively improve the image encryption effect and security，according to the study on image encryption algorithm based on chaotic system and bit operations，a image encryption algorithm based on combined chaotic system and bit operations was proposed. Firstly, the original image was decomposed into bit-planes. Considering the massive contained information of the four high-planes of the image, scrambling transformation was conducted on the four high-planes, followed by scrambling transformation of combination with the four low high-planes. Then the encrypted image was obtained by conducting exclusive or(XOR) operation between binary matrix and the combination of scrambled bit-planes. The experimental result shows that compared with the pixel location permutation (PLP) algorithm and the enhanced two-dimensional circulation encryption algorithm(TDCEA), the modified algorithm achieves a better encryption and the key space is near to 2192. It has a better security and can be against the attack of salt-pepper noise and Gauss noise. It also can- recover the original picture.