The effects of micro-alloying treatment on corrosion resistance and mechanical properties of biomaterial magnesium alloy were investigated by optical microscope (OM), scanning electron microscope (SEM), immersion test, electrochemical test, and tensile test. The results show that after successively adding Zn, Zr, and Dy, the grain of magnesium alloys is refined and the second phase is generated and grows up. When Zn, Zr, and Dy are simultaneously added into magnesium alloy, the grain size of alloy is decreased from 1087 μm to 70 μm and the microstructure becomes more uniform. Moreover, the addition of Zn, Zr, and Dy significantly improves the corrosion resistance and mechanical properties of magnesium alloy: the corrosion rate decreases from 2.01 mm/a to 0.92 mm/a; the self-corrosion current density decreases from 4.22 μA/cm² to 2.05 μA/cm²; the yield strength, ultimate tensile strength, and elongation increase from 30.5 MPa, 69.5 MPa, and 6% to 84 MPa, 154 MPa, and 8.6%, respectively.