Traditional techniques of detecting screw thread are complex processes with lower efficiency and higher cost. It has operated in such a manner as to build up an exceedingly powerful resistance to further development in modern industry. So it is necessary to establish a system of visual sensing and image processing with the code of machine visual identification technology. The basic image of screw thread could be obtained byCCD(Charge Coupled Device) and the geometrical parameter could be measured through filtering (image smoothing), edge detecting, binary image producing and contour hunting. The method to measure the tooth angle parameter of screw thread by using machine vision is discussed in this article and the measurement data is also provided at the end. The feasibility and correctness of this method has been validated theoretically and practically.