The present invention discloses an application of pentacyclic triterpenoid saponin represented by formulas (I) to (XIII) for the preparation of a medicine for preventing or treating AMPK-mediated diseases including fatty liver disease, inflammatory bowel disease, respiratory disease, diabetic complications and polycystic kidney disease. The compounds of formula (I) to (XIII) are especially usefulfor nonalcoholic simple fatty liver, nonalcoholic steatohepatitis, non-alcoholic steatohepatitis-induced cirrhosis, ulcerative colitis, Crohn's disease, chronic obstructive Pulmonary diseases, asthma,idiopathic pulmonary fibrosis, cystic fibrosis, allergic rhinitis, diabetic nephropathy, diabetic cardiomyopathy, diabetic ulcers, and autosomal dominant polycystic kidney disease. A pharmaceutical composition for preventing and treating the AMPK-mediated diseases of the present invention comprises a therapeutically effective amount of the compounds of the formula (I) to (XIII) or a pharmaceutically acceptable salt or a solvate thereof as an active ingredient and a pharmaceutically acceptable excipient.