Aiming at the weakness of Mccann99 in dealing with images,this paper develops a new method for image enhancement using Mccann99 algorithm based on Retinex theory.The initial value,D-value and the number of circle have been adjusted in the improvement.At the same time,the suitable range has been extended by the method of image expanding.The result of experiment shows that this algorithm is better than the traditional Mccann99 algorithm in enhancing image.