(Al2Ga)‐xIn (x = 0, 2, 4, 6, 8 wt%) ternary aluminum (Al) alloys with different weight ratio of In for hydrolysis H2 generation were prepared by melting‐casting technique. The phase compositions and microstructures of Al‐rich alloys were investigated by X‐ray diffraction (XRD) and high resolution scanning electron microscope (HR‐SEM) equipped with an energy dispersive spectrometer (EDS). The effect of In addition ratio on microstructures and H2 generation performance were investigated, and the hydrolysis mechanism for Al‐Ga‐In ternary Al‐based alloys has been proposed. Al phase as matrix phase in the Al‐Ga‐In ternary alloy mainly determines the hydrolysis behavior, and the second phase In strongly promotes the hydrolysis process. The increase of In content can accelerate the H2 generation rate as well as the final capacity and generation yield in neutral water. The generation yields for (Al2Ga)‐x In (x = 2, 4, 6, 8 wt%) alloys at 50°C are 0.56, 0.59, 0.62, and 0.66, respectively. The raising hydrolysis temperature can elevate the initial hydrolysis rate, final H2 generation capacity, and yield. The H2 generation capacities of (Al2Ga)‐8In alloy at 50°C, 60°C, and 70°C are 262, 290, and 779 mL·g−1, respectively.