The laser molten pool model was built to research the influence of high-frequency ultrasound vibration (HFUV) on aircraft thin-walled structures using the COMSOL software. The acoustic pressure of the laser molten pool was simulated, which considered the position and number of sources, with side-touch single vibration sources. Subsequently, we analyzed the conditions of the ultrasound cavitation effect and the acoustic streaming effect. The results indicate that, firstly, the positive and negative acoustic pressures alternate with HFUV, and this phenomenon favors the formation and collapse of cavitation bubbles. Secondly, the distance and amplitude of the ultrasound are directly proportional to the acoustic pressure of the molten pool. The acoustic pressure of the molten pool will enlarge 2-3 fold with each 10 mm decrease in the distance, which will enlarge by 10 Pa with each 4 μm increase in the amplitude. Thirdly, HFUV primarily acts as a blender toward the molten pools. The acoustic streaming effect will appear when the amplitude is higher than 7 μm and the distance is lower than 60 mm. The ultrasound cavitation effect will appear when the distance is lower than 15 mm. Fourthly, the acicular α′-martensite content is more intense, orientation and arrangement are more cluttered, besides, the acicular α′-martensite average length is shorter because of ultrasonic vibration and radiation pressure.