The sampling method is closely related to the measurement accuracy, the measurement efficiency, measurement results, error evaluation and many other factors. This paper presents a feasible method. The worm of typical entity were measured, at the same time, the measured data are processed. Helicoid surface of the worm is measured by using Coordinate Measuring Machine (CMM). The surface is measured by using two methods, one is spiral profile method, and another is tooth profile method. Comparing the parameters solved in the spiral method and tooth method is to determine the optimal sampling method.© (2010) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.