The absolute configuration at G4 of phytosterols was established by chemical method, namely:(+)-limonene with known absolute configuration was degraded through a series of steps to S(-)-5-ethyl-6-methylheptanone-2 and S(-)-5, 6 dimethylheptanone-2, which were identical with the compounds obtained from the side chain oxidative degradation of y-sitosterol and ergosterol respectively.Thus the 24刀configuration of the above mentinned sterols was established.