Laser engraving process for chemical milling is an important way of aircraft skin machining, but there is still a lack of measurement method. To solve this problem, an on-machine accuracy measurement method for chemical milling engraving lines based on laser profiler was proposed. Firstly, the kinematics model of the five-axis laser engraving machine and laser profiler was established based on coordinate transformation. The transformation between the laser measuring coordinate system and the workpiece coordinate system was determined, based on which the scanning point cloud was obtained. Then, the profile features of single frame groove section were extracted based on template matching. The width, depth and position of the groove line were solved by Levenberg-Marquardt algorithm. The contour error of laser engraving was obtained by point cloud segmentation, contour matching and contour error calculation. Finally, the effectiveness of the proposed method was verified by laser engraving on-machine accuracy test. The results show that this method can evaluate the uniformity and profile accuracy of the profile, which provides a reference for tracing the machining error, modifying the machining process and improving the contour accuracy of the engraving line.