The design of ultrasonic welding die depends on the welding object. Whether near-field welding or transmission welding, only a half-wavelength tool head can make the welding end face reach the maximum amplitude. There are two kinds of tool heads, with amplitude amplification and without amplitude amplification. The tool head of the acoustic system of plastic welding machine is usually made of aluminum alloy, and the end face is coated with cemented carbide. When the power is high, they are also made of titanium alloy, and the fatigue strength of this material is more than twice that of aluminum alloy.