This paper introduces a self-localization method depending on two signposts for onmidirectional robots. In the real environment because of keeping out or the intensity of the ray, the robot can’t find enough landmarks for self-localization. But in the past the robot needs at least three signposts for self-localization. So, depending on the advantage of the onmidirectional vision, this paper gives a new method using two signposts for self-localization. This method reduces the searching time in the Robocup competition or robot navigation. The experimental results show the method is very precise.