Abstract: In order to solve the problems existed in the traditional stereo vision and template matching method in the process of automatic guidance of the weld initial point,such as the complex algorithm,the operation of low speed as well as the low accuracy of guidance. In this paper,a method to guide the weld initial point by a monocular visual based on a specific plane was proposed. Firstly,the working plane of the workpiece to be welded is calibrated by adopting " monocular and double bits" and random consistency algorithm,and the guidance range is limited to the particular plane. Then the hand-held point laser is used as the active light source to illuminate the plane,and the camera is guided to the weld initial point under the condition of keeping the unchanged status of the camera coordinate system. At last,the 3 D coordinates of this point in the robot coordinate system are calculated to guide the robot to move to the weld initial point.