The present invention discloses doxorubicin derivatives for targeted activation by Legumain, its preparation method and use. The doxorubicin derivatives are obtained by condensation between the amino group of compound A and the carboxyl group of compound B and have the following structure: compounds A and B have the following structures, respectively: wherein R3 in compound B is Len or absent; R4 is any one amino acid selected from the group consisting of Ala and Thr; R5 is any one amino acid selected from the group consisting of Ala, Thr and Asn; R6 is wherein n=1-20; or wherein R7 is substituted or unsubstituted, linear or branched, saturated or unsaturated C1-C20 fatty hydrocarbon, or substituted or unsubstituted C6-C20 aromatic hydrocarbon. The doxorubicin derivatives of the present invention are specifically tumor-targeted and have a long in vivo metabolic half-life, as compared with doxorubicin. They exhibit an efficient and safe anti-tumor effect and could be used to prepare an anti-tumor drug.