The present disclosure relates to a tumor-targeted drug delivery system, comprising a tumor-targeted drug carrier and a tumor-treating drug, wherein the tumor-targeted drug carrier comprises full heavy-chain human ferritin. The present disclosure also relates to a method for preparing the tumor-targeted drug delivery system comprising: depolymerizing a polymerized full heavy-chain human ferritin; adding a tumor-treating drug to the depolymerized full heavy-chain human ferritin so as to bind the tumor-treating drug to the depolymerized full heavy-chain human ferritin; and re-polymerizing the depolymerized full heavy-chain human ferritin bound with the tumor-treating drug to form a nanoparticle.