With the development of society, license plate recognition systems had become an important part of intelligent transportation systems, and had been widely used. In this paper, the existing license plate recognition algorithm was optimized by the image processing technology.Firstly, by means of the collected original gray-scale image processing, three methods of color-to-gray image were proposed. Then the edge detection was carried out, and the Sobel operator was chose as the optimal edge detection method by using four kinds of edge detection operators. Finally, according to the genetic algorithm construct the method of boundary location, the license plate was located on the basis of the column scan, and accuracy rate was up to 97%.