A process of extracting polysaccharides from Inonotus obliquus, comprising the following steps: 1) putting the pre-treated Inonotus obliquus into a microwave reaction chamber, adding an organic acid or organic/inorganic mixed acid solution to the reaction chamber, then stirring well； 2) providing a microwave treatment comprising applying a microwave power, so as to separate the polysaccharide from the fruiting bodies or mycelia of the Inonotus obliquus by using the synergistic action between the microwave organic acid molecules and the organic high molecular substances of the cell wall of the Inonotus obliquus； under the microwave heating condition, most of the organic acid solution or organic/inorganic mixed acid was quickly removed by vacuum distillation, then the residual acid was removed by washing with organic solvent to complete the microwave treatment of raw material of Inonotus obliquus； 3) the microwave-treated Inonotus obliquus material is contacted with the supercritical fluid CO2, using distilled water as the entrainer, so as to obtain an aqueous solution containing the polysaccharide of Inonotus obliquus, then adding ethanol to the aqueous solution to produce a flocculent precipitate, then standing and centrifuging the mixed solution, and the precipitate is lyophilized to obtain a Inonotus obliquus polysaccharide product.一種白樺茸中多醣體的萃取方法，包括按順序進行的下列步驟：1)將經預處理後的白樺茸原料置入微波反應腔中，加入有機酸或有機/無機混酸溶液，充分攪拌使均勻潤濕；2)微波處理，施加微波功率，利用微波有機酸分子和白樺茸細胞壁有機高分子物質之間的協同作用，將多醣體從白樺茸之子實體或菌絲體上分離下來；在微波加熱條件下採用減壓蒸餾方法快速排除物料中絕大部分有機酸溶液或有機/無機混酸，而後採用有機溶劑洗滌除去少量殘餘酸，完成白樺茸原料的微波處理；3)將經微波處理過的白樺茸原料與超臨界流體CO2接觸，以蒸餾水作夾帶劑，得到含白樺茸多醣體之水溶液，往該水溶液中加入乙醇，產生絮狀沉澱，靜置後離心分離，將沉澱物冷凍乾燥，得到白樺茸多醣體產品。
