Sterol derivatives with structural formula I or II are disclosed, wherein R is defined as the description of the invention. Their synthesizing methods and anti-tumor use are also disclosed. Especially, the compound of formula I, in which R is O (i.e. the compound CL 168-6), has the anti-tumor therapeutic index of 49.3. The compound can be used to prepare a medicine for prevention or treatment of immunological diseases and cancers such as liver cancer and lung cancer.