Aiming at extracting the center position of light stripe accurately and efficiently in blue linear structured light measurement system in the complex background, a method which extracts sub-pixel center position of light stripe was proposed. According to the proportion of blue component in RGB and the property of the light stripes' intensity gradient. The method uses adaptive threshold method to obtain the light stripe's gray edge, it applies filter to decrease the error caused by non-normal distribution of strip intensity, and extracts the sub-pixel center position of light stripe by region barycenter, then rejects the error center position of light strip by connected region method. The experiment results proved that the algorithm has higher precision and stability, good noise immunity, robustness.