In this work, the effects of Hg and Ga additions on the microstructure and electrochemical properties of as-rolled Mg-Hg-Ga alloys are investigated. It can be concluded that the Mg-Hg-Ga alloys are composed of α-Mg and Mg5Ga2 phases. The addition of the Hg element not only facilitates the precipitation of Mg5Ga2 phases, but also facilitates the distribution of the Ga element in second phases. During rolling, the main soft mechanism in the Mg-1.5Hg-1.5Ga alloy is dynamic recovery, while that of the Mg-1.5Hg-2.0Ga alloy is dynamic recrystallization. The electrochemical tests reveal that the Mg-1.5Hg-2.0Ga alloy has the best corrosion resistance with the smallest corrosion current density of 0.057 mA cm−2. The Mg-2.0Hg-2.0Ga alloy is discovered to exhibit the most negative discharge potential of − 1.976 V and − 1.967 V (vs. SCE) at current densities of 80 mA cm−2 and 180 mA cm−2, respectively. It can be attributed to the fact that the increasing Hg content greatly increases the proportion of deformed grains as well as the volume fraction of Mg5Ga2 phases in the grains, improving the discharge activity of the Mg-2.0Hg-2.0Ga alloy. It also refines the grains of the alloy and forms many anodic dissolution areas, further promoting the discharge activity of the Mg-2.0Hg-2.0Ga alloy. •The Hg addition facilitates the precipitation of the Mg5Ga2 phase.•The high proportion of deformed grains deteriorate the corrosion resistance of the Mg-Hg-Ga alloys.•The Mg-2.0%Hg-2.0%Ga alloy has the best discharge performance than the other three alloys.