According to surface morphology, microhardness, X-ray diffraction, and static contact angle experiments, the changes in the surface integrity and corrosion resistance of 6061-T6 aluminum alloy after ultrasonic shot peening (USP) were investigated. Results show that the grain size of the material surface is reduced by 43%, the residual compressive stress has an increasing trend, the roughness and hardness are increased by approximately 211.1% and 35%, respectively. And the static contact angle is increased at first, followed by a slight decrease. Weighing, scanning electron microscope, and energy dispersive spectrometer were used to study the samples after a cyclic corrosion test. Results show that USP reduces the corrosion rate by 41.2%. A model of surface corrosion mechanism of USP is developed, and the mechanism of USP to improve the corrosion resistance of materials is discussed. The introduction of compressive residual stresses, grain refinement, increased grain boundaries, increased hardness, and increased static contact angle are the main factors related to the improvement of corrosion resistance in most materials, while increased roughness tends to weaken surface corrosion resistance.