An experiment of butt welding detection and localization system for robotic Metal Inert Gas (MIG) welding is introduced. The camera is attached to its stand so that it is perpendicularly positioned with the workbench. The camera was interfaced with a controller unit with two sources of light. Software for image processing (Halcon) and teach pendants were used to insert the location points for the path of the robot during welding process. The welding robot used in this study described in this paper is a KUKA KR 150 (Series 2000) manipulator robot, a 6-axis industrial robot with a repeatability accuracy of ±0.08 mm. The welding process was done by implementing an automatic conversion coordinate between camera (pixels) and KUKA welding robot coordinate (millimeters) from the ratio between the KUKA welding robot and camera coordinates. The ratio was determined by a camera and three reference points (origin, x direction, and y direction) taken around the workpiece without using any additional sensors such as external 3D measuring devices and laser scanners. Welding tests have been carried out for 4 × 4 in. with a thickness of 6-mm workpiece made from mild steel in tooth saw shape for butt welding joint configuration. The results show that the system introduced in this research can detect and locate the welding joint position where the localization errors found was less than 7 mm at the starting and ending point and 1 mm at the others points. Hence this system has advantages of the ability to perform identification without any prior knowledge of the joint shapes.