Morphologies, microstructure and composition distribution of the magnesium anodic materials were studied by metallographic microscopy, x-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). The corrosion behavior and electrochemical properties of Mg alloy were also investigated by constant current method, potential polarization, collecting gas through drainage. The results show that tin restrained β-Mg17Al12 phase precipitation along the grain boundary. With the content of tin increasing, granular Mg2Sn phase was improved. After uniform heat treatment, most of β-Mg17Al12 phase was dissolved, but most of Mg2Sn was not dissolved. Tin could improve self-corrosion potential and release hydrogen rate. Magnesium alloy anode with 1% tin content had high discharge potential and current efficiency. With the current density increasing, the release hydrogen rate augmented. The current efficiency reached 82 % at 20mA/cm2. The main composition of the corrosion products were MgO and Al2O3 which were easily peeled off. As a result, more negative and stable work potential was produced and the reaction was accelerated continuously.