Recently, there is an increasing demand for bio-absorbable coronary stent to promote recovery after operation. A magnesium alloy stent is one choice because of its biodegradable property. However, magnesium alloys have lower rigidity and lower ductility than other metals, so that an appropriate concept on designing stent structure is required to secure the radial rigidity. In this study, design parameters to actualize the AZ31 magnesium alloy stent with sufficient radial rigidity were investigated. First, the necessary radial rigidity was investigated by the comparable tests of commercially available stents. Next, the design parameters of cell struts were selected and the optimum values of the parameters to achieve the high radial rigidity were investigated by means of elastic-plastic finite element analysis. Finally, the trial model based on the optimized design parameters was produced and it was confirmed that the model had enough radial rigidity with no fracture during crimping and expansion processes.