An automatic seam tracking system used in submerged arc welding is presented. In the system, the linear CCD vision sensor is installed in front of the welding torch. Laser structure light emitted by the semiconductor laser irradiates on a slant to work-piece surface and forms a structure light strip on work-piece surface. Scatter light of the strip is received by linear CCD on top of the seam and the image information of seam can be obtained. By way of image processing and applying Fuzzy-P controller in tracking process, automatic seam tracking has been realized accurately. Anti-disturbing ability of the system to work-piece surface status has been enhanced largely by classified microadjus-tment of torch height. An automatic seam tracking system used in submerged arc welding is presented. In the system, the linear CCD vision sensor is installed in front of the welding torch. Laser structure light emitted by the semiconductor laser irradiates on a slant to work-piece surface and forms a structure light strip on work-piece surface. Scatter light of the strip is received by linear CCD on top of the seam and the image information of seam can be obtained. By way of image processing and applying Fuzzy-P controller in tracking process, automatic seam tracking has been realized accurately. Anti-disturbing ability of the system to work-piece surface status has been enhanced largely by classified microadjus-tment of torch height.