Abstract: Based on the basic principle of the sandwich piezoelectric transducer, a high-power ultrasonic horn, which can be used for the viscosity reduction of heavy oil and the pour-point reduction of high pour-point oil, is proposed and designed. The basic frequency of the horn is 16.8 kHz, and the input electrical power is 1 kW. It can work continuously in an environment of 100℃ on the industrial scale. Firstly, according to the working environment, the model of the ultrasonic horn is designed, and based on the equivalent circuit method and the transfer matrix method, the parameters of the horn meeting the resonant frequency condition are calculated. Secondly, the best working mode and frequency are determined by modal analysis and harmonic response analysis of the finite element simulation software ANSYS. According to the simulation, a prototype is made and measured by an impedance analyzer. Its basic frequency is in good agreement with the simulation calculation. The result shows that this high-power ultrasonic horn is expected to be applied in heavy oil viscosity reduction and ultrasonic sludge disintegration on an industrial scale.