To address the blockage issue of ship sea chests caused by marine biofouling, an active preventive control technology based on the 20 kHz ultrasonic cavitation effect is proposed. An ultrasonic anti-fouling device consisting of a transducer, an amplitude transformer and a vibration rod is designed, aiming to replace the traditional passive cleaning mode for mature biofilms and inhibit biofouling at the source. To further enhance the biofouling prevention performance, a barbell-shaped vibration rod composed of 18 serially connected units was developed. The synergistic vibration of these units expanded the sound field range and improved the uniformity and effective coverage of the sound field within the sea chest. Subsequently, an equivalent circuit method was employed to construct a full-link impedance matching model, and the mechanical impedances of the sandwich transducer, the stepped amplitude transformer and the barbell-shaped vibration rod were derived segment by segment. By designing parameters such as the cross-sectional ratio of the amplitude transformer and the unit length of the vibration rod, the impedances of all components were coupled and adapted through boundary conditions, which reduced energy reflection loss and realized the longitudinal resonance of the ultrasonic anti-fouling device, thereby improving the energy transmission efficiency. The multi-physics field coupling simulation results showed that the single-stage vibration rod generated a sound field with strong central intensity, weak edge intensity and obvious blind zones, while the barbell-shaped vibration rod formed a symmetric standing wave sound field with effective acoustic pressure at the edges. Its cavitation effect could disrupt the cell membranes of marine bio-eggs and planktonic larvae, thus blocking biofilm formation. Three groups of anti-fouling comparative experiments under simulated marine environments verified that the entire bottom of the chest in the blank control group was covered by organisms; the single-stage vibration rod group had a limited anti-fouling coverage, with obvious organism attachment at the edges of the chest bottom; more than 90% of the chest bottom area remained clean in the barbell-shaped vibration rod group, with only a small number of larvae attached in the corners. The designed ultrasonic anti-fouling device can realize non-contact and eco-friendly cleaning, which provides a new approach for the prevention of biofouling in ocean engineering equipment.