The invention discloses a total triterpenoid extract of inonotus obliquus with a hypoglycemic function, which is prepared through the following steps: (1) crushing and sieving inonotus obliquus, adding ethanol aqueous solution for immersion, carrying out ultrasonic extraction, separating the supernatant, and concentrating and drying the supernatant, thereby obtaining ethanol extract; (2) dispersing the ethanol extract into distilled water, oscillating and extracting with petroleum ether, and separating the extract from water-phase residues generated in extraction; and (3) oscillating and extracting the water-phase residues with n-butanol, separating the extract, mixing, concentrating and drying, thereby obtaining the total triterpenoid extract of the inonotus obliquus with the hypoglycemic function, wherein the content of the triterpenoid is 70-300mg/g. the total triterpenoid extract of the inonotus obliquus with the hypoglycemic function provided by the invention can obviously reduce the fasting blood glucose level of mouse with hyperglycemia, can significantly ease the diabetes symptoms of the mouse with hyperglycemia, and has no significant toxicity to major organs.