To solve the problems such as vascular endothelialization and restenosis caused by magnesium alloy stent, this study aims to prepare heparin (HS)/montmorillonite (MMT) coating with anticoagulant properties on biomedical magnesium alloy and investigate its corrosion resistance. Sodium montmorillonite (Na-MMT) coating was prepared on the surface of AZ31 magnesium alloy by hydrothermal method; and then HS/MMT composite coating was prepared by immersion method. The coating was characterized using scanning electron microscopy (SEM), Fourier infrared spectroscopy (FT-IR) and X-ray diffractometry (XRD). The corrosion resistance of the coating was investigated by means of electricchemical analysis and hydrogen evolution rate measurement. The results showed that the prepared HS-MMT coating was uniform and compact, with coating thickness of 41 mm. The basic elements of montmorillonite and N, S were found in the EDS analysis diagram of HS-MMT coating, and the characteristic peaks of heparin and montmorillonite were found in the FT-IR and XRD images of the coating. Compared with the AZ31 magnesium alloy, the free corrosion potential of HS-MMT coating was increased up to 0.29 V; corrosion current density was decreased by two orders of magnitude; and the average hydrogen evolution rate was 0.016 mL/(cm×h), only 18% of the AZ31 substrate. Therefore, the HS-MMT coating has good corrosion resistance, providing a new scheme for magnesium alloy vascular stents.