Abstract: Based on the theory of laser welding of plastic, the polypropylene plate was welded by laser welding, and the feasibility of laser welding of thermoplasties was ivestigated.The weld appearance showed the weld is approaching to the base metal in color. After the welding line being brittlly failed with liquid nitrogen, silver was sprayed on the fracture surface.Then the fracture surface was analyzed by scanning electron microscope, and flashes or impurities were not observed.Mechanical properties of the welded joint were tested.The mechanical properties of the polypropylene joint with laser welding was approaching to that of the base mental.It proves that laser welding is not only a feasible, but also a perfect plastics welding method.