In the case of limited transmission, the image compression transmission is completed, and the transmission efficiency of the image is maximized and the storage of the image is reduced. In this paper, CES image enhancement algorithms in DCT domain are studied in detail. The advantages and disadvantages of other enhancement algorithms in DCT domain are briefly analyzed. The problems and reasons of block effect at the junction of image blocks are emphatically analyzed. In order to ensure the visual quality of image transmission is greatly improved and block effect is effectively suppressed, an improved algorithm based on CES algorithm is proposed in this paper. The simulation results show that the improved algorithm can restrain the block effect to the greatest extent, greatly improve the visual effect of the picture, and reduce the computational complexity significantly.