Ultrasonic soldering technology, which commenced in the late 30s of last century, has been used to successfully join aluminum alloy, aluminum matrix composites, titanium alloy, ceramics and other hard to wetting materials without the assistance of flux. It is widely regarded as the most promising alternative to the flux-assisted soldering. Removing the oxide film at the interface of solder/base material is one of the most important problems for the ultrasonic soldering process. In the light of the presence of residual oxide film at the frontier of acoustic-induced solder spreading on the aluminum alloy, combined experimental and simulation analysis work was conducted to discover the characteristics and formation of the residual oxide film. Meanwhile, the elimination measure for the oxide residues was put forward. The results are of great significance to improve the quality of the ultrasonic-assisted coating, surface metallization and ultrasonic soldering.