2A12-T3 and 2A11-O aluminum alloy were welded by ultrasonic welding (USW), and then ultrasonic deep rolling (UDR) treating was performed on the welded layer. Macromorphology and microstructure of the USW layers before and after UDR were investigated by scanning electron microscope (SEM), electron backscatter diffraction (EBSD) and transmission electron microscope (TEM). Results show that UDR can eliminate the surface welded indents, decrease surface roughness and make microstructure more homogenous at the welded interface. Recrystallization occurs in the USW layer after UDR to form recrystallization texture and strain-induced grain growth, which could reduce welding residual stress at the welded interface. Therefore, UDR is favorable to improve microstructure and properties of the USW layer.