The invention relates to an inonotus obliquus deep culture method, comprising the following steps: 1. slant culture; 2. primary, secondary and tertiary seed culture; 3. deep fermentation culture; wherein, the deep fermentation culture has the following conditions: (1) fermentation culture medium consists of 0.1-10% of corn saccharification liquid, 0.1-10% of soluble starch, 0.1-5% of yeast extract powder, 0.1-5% of peptone, 0.01-1% of KH2PO4, and 0.01-1% of MgSO4; (2) fermentation cycle is 3-15d; (3) culture temperature is 20-35 DEG C; (4) initial pH value of culture medium is 4-8; (5) rotation speed of table concentrator is 50-200r/min; (6) inoculation quantity is 5-20%; and (7) liquid volume is 1/10-4/5. The invention uses fermentation engineering technology to produce inonotus obliquus, obtains quantities of reproduced strains through the primary, secondary and tertiary seed culture, makes up the defect of insufficient productivity natural bacteria, has obvious economic significance, effectively avoids contamination of microorganism as the fermentation is carried out under the aseptic condition, and provides beneficial condition for preparing the inonotus obliquus.