Al-Mg-Ga-Sn alloys with six different Al/Ga weight ratio were prepared by casting. The hydrogen production behavior of these alloys in simulated seawater (3.5% NaCl) solution at 30 ° C, 50 ° C, 70 ° C and 90 ° C was investigated, respectively, where quantitative analysis of hydrogen production rate, hydrogen yield, energy density and conversion rate, and qualitative analysis of microstructure and electrochemical performance were conducted. XRD analysis combined with SEM revealed that composition phase of Al-Mg-Ga-Sn alloys are related to the Al/Ga weight ratio. If Al/Ga＝17/1, Alss and Mg₂Sn dominate; if Al/Ga≤14/1, composition phases contain Alss, Mg₂Sn and Ga₅Mg₂. In addition to NaCl, the reaction product of Al-Mg-Ga-Sn alloy/seawater include Alss、Mg₂Sn and Al(OH)₃ at 30 °C-70 °C; and Alss, and AlO(OH) at 90 °C. The polarization resistance of Al-Mg-Ga-Sn alloy in the 3.5%NaCl solution at room temperature gradually increases as the Al/Ga ratio increases, and the corrosion current is related to the microstructure. At 90 ° C, when Al/Ga = 8 / 1, hydrogen production rate is 19.36mL / (min ? g), hydrogen yield is 1.156×10^₃ mL / g, energy density is 3.515×10^₁₀J / m^₃, and conversion rate is up to 97.6%.