The Sn−2Al filler metal was utilized to bond W90 tungsten heavy alloys by the ultrasonic-assisted coating technology in atmospheric environment at 250 °C. The effects of ultrasonic power and ultrasonic time on microstructure and interfacial strength of Sn−2Al/W90 interface were investigated. The ultrasound improved the wettability of Sn−2Al filler metal on W90 surface. As the ultrasonic power increased and ultrasonic time increased, the size of Al phase in seam decreased. The maximum value of Sn−2Al/W90 interfacial strength reached 30.1 MPa. Based on the acoustic pressure simulation and bubble dynamics, the intensity of cavitation effect was proportional to ultrasonic power. The generated high temperature and high pressure by cavitation effect reached 83799.6 K and 1.26×10¹⁴ Pa, respectively.