Abstract: The present invention relates to a novel use of a triterpenoid. In particular, the present invention provides a use of a compound of formula I, or an optical isomer thereof, or a racemate thereof, or a solvate thereof, or a pharmaceutically acceptable salt thereof, or a prodrug thereof in the preparation of a pharmaceutical composition or a preparation for preventing and/or treating ocular diseases caused by crystalline lens lesions. A novel finding of the present invention is that the compound of formula I can prevent and/or treat ocular diseases caused by crystalline lens lesions, such as prevention and treatment of cataracts, is safe, has low toxicity and few side effects, and has remarkable therapeutic efficacy and development and application prospects.