A binocular vision detection and positioning method was proposed to solve the problem of post-processing of hole support residue in metal 3D printing parts. The hole position of the workpiece was detected by the measuring system based on the arc ellipse recognition algorithm. By calculating the pose of the hole position to be machined in the optical center coordinate system of the main camera in binocular module, and converting the pose to the base coordinate system of the robot arm on machining site, the coordinate information was provided for off-line programming and automatic machining. Firstly, the binocular camera was calibrated and the measurement accuracy of the hardware system was checked. Then, the position ellipse features of the complex workpiece to be processed were extracted, and the parallel pixel acquisition and binocular matching were carried out for left and right image ellipses based on the pole-corrected images. Finally, the coordinates of matching point pairs were calculated according to the multi-view principle, and the spatial ring with coordinate information was output. A calibration target ball measurement verification experiment was carried out for binocular camera module. The results show that the measurement error is less than 0.20 mm. The measurement and positioning experiment of the actual workpiece was carried out. The results show that the maximum error of the system is less than 0.84%, the error of the center space is less than 0.50 mm, and the maximum error of the attitude of the ring is less than 0.5°.