The microstructures and corrosion behavior of the as-cast AZ91-xVN (x=0, 0.25, 0.5 and 1 in wt.%) alloys were investigated using optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical measurements. The results showed that VN can significantly refine and modify the microstructures of AZ91-xVN alloys. The corrosion resistance of the AZ91 alloy was first improved and then deteriorated with the addition of VN particles. The superior corrosion resistance of the as-cast AZ91-0.25VN alloy with the lowest corrosion rate (P_W=(1.47±0.06) mm/a) was attributed to the additional grain boundaries. With the further increase of VN content, the amount of the lamellar β-Mg₁₇Al₁₂ precipitation phase increased, and thus the galvanic corrosion between β phase and the α-Mg matrix was promoted, resulting in the deteriorated corrosion resistance of the alloys.