The invention provides a novel method for preparing optically pure substituted [(pyridyl methylene) sulfinyl]-1H-benzimidazole sulphoxide compound by enantioselective synthesis. The method requiring protection is to directly and asymmetrically oxidize prochiral thioether into a corresponding optically pure sulphoxide compound or a sulphoxide compound rich in single enantiomer by a mild and cheap oxidizing agent in the presence of a complex compound catalyst formed by an accessible and stable (+)- or (-)- tartaric acid diamide ligand shown in a general formula and titanium. Therefore, optically pure omeprazole, lansoprazole and pantoprazole can be obtained, wherein R8, R9, R10 and R11 are the same or different, and are selected from hydrogen, alkyl, aralkyl, aryl, organic polymers or a silica loading body.