Packed column supercritical fluid chromatography (pSFC) was used to resolve preparatively the four optical stereoisomers of the flavor substance of 3-methyl-γ-octalactone. First, cis-, and trans- isomers were prepared by pSFC resolution of the synthetic molecule of 3-methyl-γ-octalactone on a silica gel column. Then, the effects of kind of chiral column, type of modifier solvent and content of modifier solvent in mobile phase, column temperature, column pressure, and flow rate on the resolution of the cis-, and trans- isomers were investigated in an analytical scale. The optimum resolution conditions for cis-isomers found were chiralpak AD-H, column temperature 30 ℃, column pressure 9 MPa, 4.0 % (v/v) methanol in mobile phase, and flow rate of mobile phase 1.5 ml/min, in which the resolution factor (Rs) achieved was 1.45; while those for trans-isomers found were chiralpak AD-H, column temperature 30 ℃,column pressure 10 MPa, 4.5% (v/v) methanol in mobile phase, and flow rate of mobile phase 1.5 ml/min, in which the resolution factor (Rs) achieved was 2.24. Following the optimum chromatographic conditions, preparative resolution of cis-, and trans- isomers of 3-methyl-γ-octalactone were performed further by pSFC, and four stereoisomers of several milligrams were obtained all in an optical purity of 100 % e. e.