Sacrificial anode cathodic protection is one of the most important corrosion protection methods for deep-water steel structures. The electrochemical performance of sacrificial anode in deep-water environment directly affects the protection effect and service life of the facilities. By means of the cathodic protection test device and data acquisition/storage system installed on the 1 200 m Deepwater test rack in the South China Sea, the free Running Test (FRT) was applied to study the electrochemical performance of sacrificial anode under the 110 days cycle condition. Solution morphology, electrochemical capacity, current efficiency and other performance of 3 kinds of composition Al-Zn-In-based sacrificial anodes were compared under the environmental conditions in the South China Sea, providing a reliable reference for the cathodic protection design of deepwater subsea engineering facilities.