Abstract: In the production and processing of automobile parts, the perpendicularity measurement between the center line of threaded hole and the designated plane must have the characteristics of high efficiency, accuracy and convenient use, so as to meet the needs of industrial automation, intelligence and low cost in automobile production. In order to realize the on-line automatic detection and sorting in the production process of automobile filter sealing plate, this paper designs a detection system of thread hole perpendicularity based on the symmetrical measurement method of double cameras, which is used to automatically detect the thread hole perpendicularity and realize the automatic classification of qualified products and unqualified products. Two coaxial cameras are set symmetrically in the system. The far and near circular surfaces of the threaded hole are collected from the front and back sides respectively, and the center coordinates are extracted. The perpendicularity of the hole is calculated according to the deviation of the two center coordinates. The measurement method of symmetry evaluation is applied in the system, and the measurement accuracy can be 0.100 mm, which meets the accuracy requirements of system design.