In order to solve the Self-localization problem in highly dynamic situation in the RoboCup Middle Size League competition, a fast robot self-localization method was used. Firstly, according to the structural of Omnidirectional visual robot during visual processing, using an image mask to remove the invalid information. In order to avoid searching for all the pixels and narrow the scope of pixel, a method based on Bresenham algorithm was used. Using white line positioning algorithm to determine the robot position, combined with the search method based on Bresenham algorithm, effectively improve the real-time image processing. Finally, design a test based on ASROⅡ robot and it is proved reliable and effective.