Abstract: The two diastereomers ( designated as Aand B ) of Triadimenol were separated and the enantiomers of the active triadimenol Awere further resolved. The absolute configuration of (+)-triadimenol Awas determined both by Horeau method and X-ray diffraction method. Its oxidation to the corresponding (+)-triadimefon was successfully carried out for the first time by Jones' oxidation. The asymmetric reduction of (+)triadimefon was carried out by using an hydrogen transfer mechanism of Grignard reaction to obtain different optical isomers of triadimenol.The preliminary bioassay on mixed spores of wheat rust indicated that among the four optical isomers of triadimenol, (-)-A-lS,2Renantiomer has the highest bioactivity, whereas both levo- and dextro- isomers of triadimefon do not differ much in their bioactivities.