The invention discloses camptothecin and a self-emulsifying medicine precursor of a derivative thereof. The self-emulsifying medicine precursor is prepared by the covalent union of medicine molecules and hydrophilic radicals, wherein the medicine molecules are camptothecin molecules or camptothecin derivative molecules, and the medicine carrying quantity of the precursor is as high as more than 50%. The invention also discloses application of the self-emulsifying medicine precursor. The self-emulsifying medicine precursor can form micelles or vesicles with nano size in water, can be used as a medicine carrier used for loading one or a plurality of other anticancer medicines, such as CPT derivatives, yew alcohol, turmeric essence, methotrexate, irinotecan, danshinolic acid, matrine, doxorubicine and the like, can form a nano medicine carrying a plurality of medicines and can realize the synergic treatment of the medicines.