Abstract: As for the process control of the arc welding,a detection system for welding process was proposed based on passive vision,which was composed of industry CCD camera,narrow-band optical filters and computer.The center wavelength of the narrow-band optical filter was 950 nm,which could reduce the arc interference and help to obtain a clear image of in welding process.During the welding,the system can detect the arc,molten pool,wire in real time,and the characteristic parameters of the position deviation,amplitude deviation and angle deviation of the arc can be obtained.According to the obtained information,the welding torch can be controlled to make the arc move,which can make the swing center,the swing plane and the swing amplitude be adapted to the position and shape of the weld seam,avoid defects formation during welding and result in a good welding quality.