Abstract:In the recent years, The pharmaceutical manufacturers interest to natural medicines and biological active preparations from animal, plant and mineral raw materials. According to some sources, Plantago majus contains polysaccharides and aucubin. Some researchers investigated aucubin that is anti inflammation and antimicrobial activity. Many anti cough formulations that are contains Plantago majus sold in pharmaceutical market. For example: Herbion, Pectoral manufactured by KRKA, Naturwaen and Mepha, respectively.The aim of this study determination of aucubin and biological active substances in Plantago majus that is growth commonly in Mongolia.The result of this study, Plantago majus leaves are estabilished polysaccharide 4.66%. Leaves of Plantago majus has been extracted by water(1:5), water (1:10), 30 % sorbitol and 20% ethanol, then determination aucubin and polysaccharide. The results, polysaccharide was 4.12%, 3.46%, 0.336% and 2.65%, respectively. Aucubin was 2.88%, 3.44%, not determined 30% sorbitol extract and 1.88%, respectively.