Fuzzy enhancement algorithm and KSW entropy algorithm are proposed for pre-welding seam image segmentation. Before automatic welding, the welding seam image is often segmented so that it can be recognized by robot. KSW entropy algorithm is an effective way for segmentation. Image enhancement is often applied before segmentation in order to get better result. As the pre-welding seam image is not uniform, the effect is not ideal after applying regular enhancement algorithm and KSW entropy algorithms to it. Fuzzy enhancement algorithm can eliminate the noises and preserve the details of the image intelligently. The image dividing point has close relation with the result of fuzzy enhancement algorithm. Self adapting algorithm about how to get the proper image dividing point is discussed. When fuzzy enhancement algorithm and KSW entropy segmentation algorithm are used to pre-welding seam image, the experiment results prove that the best effect can be got and little time will be cost.