The visual sensing technologies based on the laser structured light are the main technical means and foundation for the realization of welding groove detection, seam tracking and robot path planning in the welding industry. Their technical advantages applied in the welding industry are introduced, the basic detection principles are analyzed, and the research focuses and developing directions in the welding industry are concluded and summarized. Through discussion on the operational principles and characteristics of various visual sensors based on the laser structured light, the comprehensive summary and a novel classification are proposed, and their respective technical characteristics and research progress are introduced in detail. Finally, the existing problems of visual sensing technology based on the laser structured light are discussed in order to promote further research and application of this technology.