The invention discloses an application of cedrelone and a pharmaceutically-acceptable derivative thereof to prepare a medicine resisting cryptosporidium baileyi. Cedrelone and a pharmaceutically-acceptable derivative of cedrelone together with an acceptable auxiliary material are made into powder, the power is added to feed, uniform mixing is carried out, and chicken are fed with the obtained product at a daily feed amount, or cedrelone is made into water-soluble cedrelone power, the obtained powder is dissolved in water, the chicken are fed with the obtained product at a daily drinking amount. It is proved by animal infection experiments that cedrelone reduces ovulation sacs infected with cryptosporidium baileyi by no less than 76.6%. Cedrelone has a good effect on cryptosporidium baileyiresistance.