The invention discloses biomedical material and a preparation method thereof. The preparation method includes: 1, melting and forming; 2, polarizing an anode; 3, depositing the anode; 4, performing thermal treatment; 5, coating. The biomedical material comprises a pure magnesium or magnesium-alloy base and a functional film which covers the surface of the base and which has the functions of degradation protection and self-degradation. The biomedical material features controllability, full degradation and full absorption, and the strict requirements for ideal features of the degradable biomaterial are met. The biomedical material has the advantages that an optimal solution is provided for the absorbable biomedical material, especially the contradiction between biodegradability and degrading speed control in medical magnesium alloy, and related materials and techniques are applicable to common medical instruments and are more competitive in production of high-end medical instruments, such as implant instruments, especially 'secondary-operation-free' implants.