In order to meet the requirement of seam finder and seam tracking under special conditions, using laser scanning technique, seam tracking system based on circular laser sensor is developed, cooperated with welding robot, built “hand-eye” system, and three-dimensional information for weld workpiece could be extracted, escaped from shortcomings of less information, ambiguous explanation and single tracking direction for “spot” or “line” laser trajectory. Study on calibration of vision sensor for seam position and seam tracking is carried out. Finally, real experiment for butt joints, lap joints and corner joints was carried out and the calculation precision was analyzed. The results showed, the pattern of the circular laser is different for different seam, combining with calibration results, the three-dimensional coordinates of welded joints could be determined and the precision could meet the requirement of seam tracking test.