Abstract: Ultrasonic vibration effects on the microstructure and macro-segregation of 7050 aluminum alloy were investigated by adopting various ultrasonic powers to the aluminum melt. It is found that cavitation effect and acoustic streaming effect, caused by ultrasonic vibration, play a major role in the solidification process. A reasonable ultrasonic power can obviously refine the grains, optimize the microstructure, and improve the homogeneity of solute elements. The maximum decrease of the macro-segregation level occurs at the power of 170 W, and the segregation index values of Zn, Mg, and Cu are 0. 059 3, 0. 056 5, and 0. 031 9, respectively. Exceeding the power of 170 W, the rich level of solute elements in the ingot center enhances greatly and the macro-segregation level increases.