The treatment of large-area bone defects has the risk of poor healing, and the development of implantable materials that have both mechanical adaptability, biological activity and degradability is a clinical difficulty. In this study, a 3D-printed porous tantalum scaffold with elastic modulus near human bone and a metal magnesium with excellent biological activity was prepared by a pressure-free impregnation process. We then conducted a comprehensive evaluation of the material's characterization, mechanical properties, degradation process, and its impact on MC3T3 cells. The results show that the composite phases of the composite are Ta and Mg phases through SEM and EDS. In the compression experiment, Ta-Mg composite showed higher strength compared with porous tantalum. In vitro experiments, the composite material has good biological activity. The degradation results show that the Mg2+ concentration of the composite material is more suitable for cell growth, and the tantalum scaffold always keeps the substrate intact throughout the degradation process. By implanting rabbits in vivo, the in vivo results show that Ta-Mg composite has stronger biological activity, so its excellent in vitro and external osteogenic properties and degradation characteristics will provide new strategies and methods for the development of next-generation customizable bone repair implant materials.