In this paper, a sub pixel center extraction method is proposed based on dual frequency curve fitting. First, twice threshold method is used to automatically segment light stripe region, and gray-gravity method is used to obtain the initial position of the light stripe region. Then, a normal moving linear fitting is designed to obtain the local normal of light strip curves. Finally, the sub-pixel center coordinate of the light strip is extracted precisely through dual frequency curve fitting of pixel data in the normal direction. Experimental results show that this method can partially eliminate the influence of high-frequency noise. Compared with Steger method, the root mean square error of the strip center extracted by this method is less than 0.1 pixel, and the speed is about 26 times of it. This method can be applied to the extraction of light stripe center of various materials, which provides a reference for the extraction of laser stripe center in industrial applications.