Abstract: During automatic welding for small batch, the generating process of welding path is complex. Aiming to solve this problem, the automatic welding equipment with the workpiece whose welding seam is in plane was developed, and a method was proposed that the welding path of shaped workpiece was generated on-line based on machine vision system. The contour figure of the shaped workpiece could be extracted through image recognition algorithms, and the welding path would be generated on-line after least square method applied to NURBS curve fitting. The results show that the algorithm can generate online the smooth welding path for any shaped workpiece quickly with high degree of precision and efficiency, and the welding jitter can be avoided and the welding quality can be ensured.