Abstract: An automatic weld seam detection algorithm is proposed in this paper. The main direction of the pipeline is determined by the gradient-direction histogram, which saves huge amount of computation comparing to the traditional algorithm. The saturation in the HSV color space is adopted to enhance the feature of weld seam which increases robust of detection and the precision of the weld seam localization. A series of experiments show that our algorithm achieves high accuracy in the weld seam detection and localization.