In order to realize the fully independent mobile derusting of splice welds on the ship wall, a kind of laser vision weld identification method is proposed based on the three-line laser structure light. In view of the crisscross hull splice welds, according to the characteristics of three-line laser, five variables are defined characterizing the laser shape and laser stripe spacing, the change rules of characteristic parameters of three laser stripes at the weld intersections are summed up,and the unified identification model for the cross-shaped and T-shaped weld crosses is established. The experiment verifies that it is better in the anti-interference and more abundant in the amount of information to employ the three-line laser, and it can accurately identify the weld joint cross type under the various working conditions, which lays a foundation for the follow-up weld real-time tracking and trajectory planning.