Ultrasonic metal welding can be used to weld different metals together safely and precisely, without solder, flux and special preparation. Ultrasonic metal welding machine consists of a power supply, a transducer, a booster and a horn. This paper designed the horn needed for Ultrasonic metal welding. The horn has to be designed and manufactured accurately, because measurements such as the shape, length, mass and etc. have effects on the resonant frequency and the vibration mode. The designed horn has the feature of 40,000Hz of nature frequency, and maximizes vibration range in the Tip by resonance in the frequency of ultrasonic wave machine. In this paper, we calculated and analyzed the natural frequency to find the optimal design of the horn that had the amplitude about $12{mu}m$ by the modal analysis and harmonic analysis using ANSYS. And we analyzed FFT analysis of the manufactured horn.