The non-contact measurement of space surface profile based on line laser is an effective method for the accurate on-line dimension detection of present industrial parts. In order to improve the non-contact triangulation accuracy, we need extract the section characteristic line of measured contour accurately. However, for the surface of industrial parts with irregular surface, it is difficult to express the contour feature accurately with a simple smoothing processing method. Therefore, a polynomial curve fitting method is proposed, which takes the contour feature points as the boundary points and then puts all the points together to produce a continuous contour curve. By comparing the collected data set of tested objects and corresponding fitted curves, we find that the proposed method can not only solve the jagged problem generated in the laser line extraction process, but also can improve the measurement accuracy. The fitted curve can truly express contour features of tested surface, which has important practical value.