Effects of Ga on the electrochemical properties of Al-Zn-In sacrificial anodes in 3% NaCl solution were investigated by means of electrochemical techniques, atomic spectrum and electron-probe experiments. The distribution and the role of alloying elements such as Ga and In in the active-dissolving process of Al-Zn-In sacrificial anodes were analyzed. The results show that Al-4%Zn-0.022%In-0.015%Ga is a kind of ideal sacrificial anode with its operating potential of (-1 039) mV (SCE) and current efficiency of 96.3%. With the increasing of Ga amount while the other alloying elements are unchanged, potentials of aluminium-based alloys shift negatively but their current efficiency drops down and pitting corrosion increases evidently. Gallium distributes homogeneously in the alloy while indium gathers locally. Because of the activing effect of In~(3+), the surface passivated membrane is destroyed, potentials shift negatively, and with In~(3+) and Zn~(2+) together, Ga~(3+) promotes the aluminium alloy to dissolve actively.