A method for depth measurement of scratches on the curved surface using light-sectioning method is presented, which can improve the accuracy of scratches measurement compared with traditional light-sectioning method. The shortcomings of the traditional light-sectioning method were analyzed and the error of the scratches measurement on the curved surface was modeled and simulated. The results of the analysis and the simulation show that the error of the scratches on the curved surface varies with the radius of curvature and the width of the scratches using traditional light-sectioning method. The precision parts with different radius were selected in the experiment and the scratches on the curved surface were measured. Comparing with the large error of the conventional light-sectioning method, the accuracy of the results measured by this new method is higher when the radius of curvature is smaller and the width of the scratch is larger. The error of measurement less than 1mm can be reduced by this new method when the radius of curvature is less than 10 mm and the scratch width is greater than 283 mm. This method can be applied to the depth measurement of scratches on the curved surface of the precision instrument.