: Pleurotus ostreatus (Jacq) P. Kumm) is the second cultivated and most popular edible mushroom after Agaricus bisporus in the world. The fruiting bodies of these mushrooms have high nutritional value and are beneficial for health. Pleurotus ostreatus are an interesting source of bioactive glucans and other polysaccharides. This study focuses on the isolation and structural characterization of glucans from the fruiting bodies and stems cultivated mushrooms Pleurotus ostreatus. Methods: Physicochemical properties of fruiting bodies and stems cultivated Pleurotus ostreatus in Mongolia, were studied using standard methods. Glucans were extracted and purified using the precipitation method and Sevag reagent, and functional groups were determined by FT-IR. Conclusion The characteristic absorption bands of the water and alkali-soluble fractions were found near 1070, 1044, 869 and 777-769 cm-1. These IR bands are characteristic of fungal (1→3)(1→6)-β-D- glucans, and indicating these fractions are glucan-type polysaccharides