The wheel set is the major running component of a train. Online measurement of wheel set wear parameters is important for train safety. Acquiring a completely structured light projection image is important to wheel set profile dynamic inspection method.We develop a new image segmentation algorithm based on region growing. According to the characteristics of wheel set images acquired in different conditions and the location of their base points

a new growth standard of the algorithm is proposed. The wheel set profile images are extracted effectively through proper seed selection and growth process. By processing a series of images with severe noise and external disturbances

the overlap area ratio is more than 80%

and the error segmentation area ratio is less than 0.02%. The wheel set profile curves can be extracted effectively based on the new algorithm.