At present, the pouring riser of valve castings is mainly removed by manual cutting, polluting the environment and causing harm to the human body with a low efficiency. Therefore, an automatic cutting pouring riser method using the stereo vision system and manipulator is proposed. The relative position of the valve casting and the end of the manipulator is obtained through the position transformation of the valve casting coordinate system, the manipulator end of the coordinate system, and the camera coordinate system. The spatial motion trajectory of the manipulator is planned, implementing automatic pouring riser cutting of the same valve casting with the same pose. The experimental results show that the position deviation and the angle deviation of the repetitive positioning accuracy and the random positioning accuracy of the visual system are within ±1 mm and ±1°; in the pouring riser cutting test, the maximum deviation between the actual cutting trajectory and the theoretical cutting trajectory is 3 mm. In summary, the method shows a good reliability and could meet the requirements of cutting accuracy.