This paper presents a license plate recognition system based on the computer vision, including five parts which are image pre-processing, license plate locating, character segmentation and recognition. In the image pre-processing part, the RGB images obtained from the camera are changed into the gray images. After the gray images are changed into the binaries images, and the noises are filtered by using the median filter. In the license plate locating part, we predict the possible location of the license plate in the binaries image and acquire it with using the length and width value of the general license plate. In the character segmentation part, the characters of the license plate are segmented due to the high contrast between those and the background. At last the neural network is adopted into the pattern recognition, and the letters and numbers could be recognized. Moreover, we exploit the Bottom-hat module to enhance the features of the license plate in order to promote the identification significantly.