Aiming at the assembly work of robot base and first axis gear reducer in industrial robot body production line, this paper proposed a visual recognition algorithm based on improved Hough transform of circle detection algorithm. The proposed algorithm could accomplish the rapid recognition and positioning of workpiece with high precision. Combined with the application of heavy-load industrial robot, the whole system realized the intelligent assembly of robot base and first axis gear reducer. That is 'manufacturing robot with robot'. Finally, the feasibility and reliability of the algorithm is verified by experiment.