Ultrasonic plastic welding refers to that, under the moderate pressure of the ultra-high frequency vibration welding head, the joint surface of the upper and lower pieces of plastic will generate friction heat and instantly weld. The welding strength can be comparable to the body. With appropriate workpieces and reasonable interface design, water and air tightness can be achieved, and the inconvenience caused by the use of auxiliary products can be eliminated, so as to achieve efficient and clean welding.