The work aims to improve the strength and corrosion resistance of micro-arc oxidized biomedical magnesium alloys. Silane coupling treatment and poly-L-lactic acid (PLLA) sealing treatment were used to modify the surfaces of micro-arc oxidized (MAO) AZ31B magnesium alloy wires. Effects of silane coupling and PLLA sealing treatment on overall performance and degradation behaviors of MAO-wires were investigated by using scanning electronic microscopy (SEM), energy dispersive spectrometer (EDS), tensile tests and in vitro immersion tests with simulated gastric fluid (SGF). Silane coupling treatment to MAO-wires might improve the PLLA sealing effects. The corrosion resistance of the treated wires increased first and then decreased as the coupling time increased. The treated wires showed best corrosion resistance when the treatment lasted for 90 min. Corrosion resistance of the treated wires increased firstly and then decreased, and the strength increased as the PLLA concentration increased. Both the corrosion resistance and strength increased gradually as the pulling speed increased. Both the corrosion resistance and strength decreased gradually as the dipping times increased. The PLLA sealing treatment had no effects on the elongation of the treated wires. The treated wires showed the best overall performance when the PLLA concentration was 0.14 g/mL, the pulling speed was 0.9 cm/s, the dipping time was only one time. Corrosion resistance of the micro-arc oxidized (MAO) AZ31B magnesium alloy can be improved by poly-L-lactic acid (PLLA) sealing treatment effectively, and the effects relate to the concentration of PLLA, pulling speed and dipping times. The PLLA sealing effects can be improved by silane coupling treatment to MAO-wires.