The effects of combined C2Cl6 degasser and ultrasonic treatment on the hydrogen content in the Al-3.06%Si, Al-3.21%Mg and 2024 aluminum alloys and the mechanical properties of 2024 aluminum alloy were studied. The results show that the degassing time with a single ultrasonic treatment is greatly shortened by the combined treatment. Furthermore, the mechanical properties of the 2024 alloy are also significantly affected by the combined treatment: the tensile strength and elongation are increased by 28.3% and 92.3% (maximum increase), respectively, compared with those without any treatment. However, the yield strength is slightly affected by the degassing treatment (with an increase of only 6.7%, maximum increase). In addition, with the degassing treatment, the fracture mode is transformed from brittle fracture to microvoid coalescence fracture, improving the mechanical properties of the alloy.