Abstract: The basic principle of rotating arc sensor extraction for welding seam deviation was introduced.In order to reduce the influence of weld pool disturbance on the welding current,a sampling method of the welding current signals-'Sample a quarter of the circle' was proposed and the implementation process of sampling was analyzed.A new signal processing method for carbon dioxide gas arc welding current was also proposed,and the basic principle and calculation steps were analyzed.On the basis of the method,the weld seam deviation signal for space curve was received.The results showed that the extraction for welding seam deviation based on 'Sample a quarter of the circle','Double analog filtering' and 'Exponential smoothing digital filter' could be applied in the seam tracking.