To improve the wettability of hypereutectic Al-60Si alloy and enhance the mechanical properties of the joints, Al-60Si alloy was joined by ultrasonic soldering with Sn–9Zn solder, and a sound joint with in-situ Si particle reinforcement was obtained. The oxide film of Al-60Si alloy at the interface was identified by transmission electron microscopy (TEM) analysis as amorphous Al₂O₃. The oxide of Si particles in the base metal was also alumina. The oxide film of Al-60Si alloy was observed to be removed by ultrasonic vibration instead of holding treatment. Si particle-reinforced joints (35.7 vol.%) were obtained by increasing the ultrasonication time. The maximum shear strength peaked at 99.5 MPa for soldering at 330 °C with an ultrasonic vibration time of 50 s. A model of forming of Si particles reinforced joint under the ultrasound was proposed, and ultrasonic vibration was considered to promote the dissolution of Al and migration of Si particles.