The utility model provides a plastic light pipe, relate to the laser welding technology field, prepare the light pipe that has lens through utilizing such as low price materials such as general transparent material, with the principle that assembles light based on convex lens, light source emission's laser will be swashed and back formation welding facula will be handled, and accessible adjustment light pipe and laser source and by the distance between the weld, the relative position isoparametric, the shape of feasible welding facula and the demand that the energy homoenergetic enough satisfies welding process, and then realize the laser welding by weld, be the light pipe low in cost not only in this application, and the welding facula energy that assembles is even, when reducing producer's technology cost, can the effectual performance that improves laser welding process.