Porous magnesium (Mg) scaffolds were successfully prepared by 3D gel-printing (3DGP) technology in this study. Absolute ethanol and epoxy resin were mixed to prepare the premixed solution and then Mg powders were mixed into the premixed solution to prepare the slurry which was used to print Mg scaffolds by 3DGP. After debinding and sintering, the properties and microstructure of the samples were tested. The scaffolds were implanted into the femoral condyle of rats, and the implanting position was observed at the first, the third and the fifth week. The results showed that the highest compressive strength of Mg scaffolds can reach 20.05 MPa at a porosity of 64.4% after sintered at 610 °C. In order to study the degradation and osteogenesis of the scaffolds, pure Mg, oxide-coated Mg and TCP scaffolds were implanted into the femoral condyle of rats and compared with the blank control group. The results showed that oxide-coated Mg scaffolds have relatively good biocompatibility and degradability. According to the results of CT (Computed Tomography) and X-ray, the oxide-coated Mg scaffolds can promote cancellous bone osteogenesis and can delay the degradation of pure Mg scaffolds.