To improve the processing and practical performance during the manufacture of complex thin-walled parts, the mechanical properties and microstructure revolution of complex thin-walled parts of 6061 aluminum alloy prepared by ellipse bidirectional vibration incremental forming were investigated. The traditional incremental forming, vertical unidirectional ultrasonic vibration incremental forming, and ellipse bidirectional ultrasonic vibration incremental forming methods were compared. To verify the enhancement effect on forming quality and mechanical properties of complex thin-walled parts of aluminum alloy, the microhardness and residual stress of as-prepared parts were analyzed, and their morphologies were observed. The microhardness test results show that the ellipse ultrasonic incremental forming process can soften the material and improve its plasticity and toughness, thereby promoting the formability of thin-walled parts of aluminum alloy. A great number of dimples appearing on the fracture surface further confirms this conclusion. The microstructure characteristic on the surface of as-prepared parts shows that the ellipse bidirectional vibration incremental forming method can significantly improve the surface quality. In addition, the ellipse bidirectional ultrasonic vibration incremental forming method can form a residual compressive stress layer on the surface of 6061 aluminum alloy, which improves the fatigue resistance performance of complex thin-walled parts.