According to the principle of processing, a non-contact photoelectric detection method for double-enveloping hourglass worm is investigated. The structure of the detection system is designed. It consists of solid-state image sensor CCD and light source. The parallel light source is installed on a sliding-board which is fixed on the rotary table. There is an inclination angular β between the parallel light source and the plane of the work table. The industrial CCD lens is mounted on the other side of the worm through a frame. The plane of the CCD is vertical to the parallel light source. Therefore CCD imaging is along with the direction of the generating process surface. By comparing the measured spiral tooth surface with the standard spiral tooth surface, the manufacturing error of worm can be calculated. Manufacturing accuracy of the worm can be obtained. Based on the four-axis CNC grinder, Non-contact photoelectric detection method is studied through preliminary experimental study. The experimental results indicate that this method is feasible in the precise detection of the double-enveloping hourglass worm.