Laser centerline extraction of line structured light is one of the key technologies in three-dimensional measurement of line structures light, and its extraction accuracy has an importantimpact on the measurement accuracy of the system. In actual 3D measurement, the image captured by the camera is affected by various factors such as the surface reflectivity of the object, which increases the difficulty of extracting laser centerlines. To address this issue, an improved extraction method combining grayscale centroid method is proposed. This method is based on connected domain analysis to remove background light bars and noise areas, and then implements local morphological processing based on linewidth distribution. Finally, the sub-pixel position of the laser centerline is calculated using the grayscale centroid method. The centerline calculation accuracy of the proposed method has improved by about 60% compared to traditional method. It can still accurately extract the position of the laser centerline in areas with overexposure and underexposure in stripe images, which can adapt to the test of complex environments and ensure the stability and accuracy of the laser centerline extraction work.