Abstract: In order to improve the intelligent level of remote welding, a stereo vision system was designed to reconstruct the 3D environment of the welding robot. The system was calibrated in two steps. First, a plane pattern based method was used to calibrate offline the intrinsic parameters of each camera and the relations between the two CCD cameras were unchanged during the process. Then the relationship between the camera coordinate system and the robot coordinate system was calibrated on line using a linearmethod. The result shows that the mean error of the reconstruction results is smaller than 1 mm, and the max error is smaller than 3 mm.