This paper is to analyze the electrochemical performance of A13 Al-Zn-In-Si sacrificial anode in seawater and sea mud. The four-day galvanostatic polarization acceleration test was carried out by constant current polarization. The electrochemical corrosion process was analyzed by electrochemical impedance spectroscopy (EIS). The corrosion morphology and surface chemical composition were presented by scanning electron microscope (SEM), energy spectrum analysis (EDS) and three-dimensional depth of field microscope. The corrosion morphology and electrochemical performance of Al-Zn-In-Si sacrificial anodes under simulated seawater and sea mud environments were comparatively studied. In the simulated seawater and sea mud environment, although Al-Zn-In-Si sacrificial anode met the requirements of DNVGL-RP-B401, the electrochemical efficiency in the sea mud environment was only 65.97%, far lower than 89.43% in seawater environment. The sacrificial anode showed uniform corrosion in seawater environment, but severe non-uniform corrosion in sea mud environment, and the surface corrosion pits were loose porous honeycomb. In the sea mud environment, the corrosion products of the Al-Zn-In-Si sacrificial anode are difficult to diffuse, the corrosion pits appear locally, and the self-corrosion rate is high, resulting in the decrease of electrochemical efficiency. In the dissolution process, the self-consumption increases due to tissue abscission, The decrease of electrochemical capacity leads to the lower electrochemical performance of anode in simulated sea mud than that in seawater environment, and reveals the corrosion mechanism of anode in simulated seawater and mud environment.