The effect of Mn addition on the microstructure and corrosion behavior of extruded Mg-Zn-Y-Nd alloy immersed in 3.5 wt.% NaCl solution were studied by optical microscope, scanning electron microscope equipped with energy dispersive spectroscope, X-ray diffraction, immersion, and electrochemical measurements. Results suggest that the Mn addition in the studied Mg-Zn-Y-Nd alloy can induce Mg3Y2Zn3 (I-phase) precipitation which may inhibit dynamic recrystallizaiton (DRX) grain coarsening during hot extrusion. Meanwhile, its corrosion resistance was improved owing to the addition of Mn. The corrosion rates of free and 1.0 wt.% Mn containing Mg-5.6Zn-1Y-0.4Nd alloys were 18.78 and 9.89 mm·y?1, respectively. The improvement of corrosion resistance is mainly due to an enhanced protectiveness of the corrosion product layer.