A binocular stereovision system with a linear laser emitter is developed to detect seam position and its orientation, employing acquired 3-dimensional seam data, the automatic teaching of welding robot is implemented using a controlling strategy based on ant colony optimization(ACO) algorithm, in which the angle increment of robot joint is discretized as the nodes of ACO graph and a corresponding pheromone updating strategy is presented. The experimental results for curvilinear seams and saddle-shaped seams show that the automatic teaching of welding robot can be successfully completed using the ACO-based controlling strategy under the guidance of stereovision, and the welding trajectory generated by the proposed method has higher accuracy and less setting time compared with conventional proportional-integral-differential (PID) controller and fuzzy controller.