Aimed at highlighting the variety, quantitative of tiny scratches on the metal surface is difficult for the accurate detection problem, a solution based on linear laser and (CCD) combined measurement is presented.Firstly, the line laser was applied to the metal scratch surface; secondly, the highprecision CCD camera was used to collect the image of the scratch and the line laser; then, the Smoothing Spline function was used to fit the smooth Spline; and then a piecewise linear interpolation was carried out. Finally the scratches on metal surface were transformed in to lowhigh difference graph to obtain the width and height of scratches. This method was mainly to find the geometric center of the scratch and to replace the scratch with lines, so as to analyze and calculate the width and depth characteristic parameters of the scratch. The experimental results have a width error of less than 005 mm and a depth error of less than 01 mm for the scratch detection, proving that this method can effectively identify metal surface scratches, and has obvious advantages in accuracy and segmentation efficiency, and can meet the actual measurement requirements of the scratches on the surface of the axle of CRH.