S-PG05 ((15S)-15-methyl-prostaglandin F-2 alpha methyl ester) was separated from the epimer R-PG05 and other impurities using SMB, combined with batch chromatography. Based on this technical procedure, 94% pure S-PG05 was obtained. Different column configurations and separation conditions of SMB have been selected. A non-synchronous shift with a "partial extract withdrawal'' strategy has been employed, resulting in the saving of desorbent and the increase of the purity of S-PG05.