Abstract: In this paper,a method to detect the welding pool width based on the specular reflection physical characteristics of a welding pool during TIG welding of Q235 steel was investigated. The combination of spatial filtering and frequency domain filtering was applied to eliminate the disturbance in a welding pool image which was polluted by the high frequency noises. In comparison with spatial filtering,using the low pass of frequency domain filtering and the compensation of high frequency enhancement filtering could better eliminate the welding pool image noises. The arc welding experimental results show that the welding pool width could be extracted accurately by the proposed identification algorithm.