Compact conversion coatings with much better corrosion resistance for Mg-8.5Li alloy were obtained by immersing in a solution of permanganate. The concentration of potassium permanganate was discussed. The surface morphology of the conversion coatings was observed by scanning electron microscopy (SEM), and the chemical composition was characterized by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The corrosion resistance of Mg-8.5Li alloy and permanganate conversion coatings were investigated by means of potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and mass loss measurement. The results show that the coatings with cracked morphology are homogeneous and uniform. The corrosion resistance of permanganate conversion coatings is improved greatly compared with that of Mg-8.5Li alloy. When the concentration of permanganate is 4.0 g/L, the corrosion current density is the smallest, capacitance arc is the biggest and corrosion rate reaches minimum and the conversion coating presents the best corrosion resistance behavior.