This research is aimed to develop a kind of poly(ethylene glycol) shell-sheddable magnetic nanomicelle as the carrier of doxorubicin (Dox) in order to enhance its cellular uptake ability, and achieve synchronous magnetic resonance imaging (MRI)-visible function. Firstly, the five-member rings in poly (L-succinimide) (PSI) were successively opened by the amino terminated disulfide-linked poly(ethylene glycol) monomethyl ether (mPEG-SS-NH2) and dopamine (DA) to produce the graft copolymer of mPEG-SS-NH-graft-PAsp-DA. And then, drug-loaded magnetic nanomicelles of mPEG-SS-NH-graft-PAsp-DA@Fe3O4.Dox were obtained by the Fe3O4 nanoparticle-induced self-assembly of mPEG-SS-NH-graft-PAsp-DA. These magnetic nanomicelles showed spherical shapes with average particle size of about 120 nm measured by dynamic light scattering (DLS). Due to the detachment of PEG shell in the presence of dithiothreitol (DTT), the magnetic nanomicelles showed accelerated in vitro release of Dox, and enhanced cellular uptake ability. Compared with free Dox, the Dox-loaded magnetic nanomicelles showed essential decreased cytotoxicity against Bel-7402 cell line. If its high r2 relaxation rate (221 mM(-1) s(-1)) and good negative contrast effect for magnetic resonance imaging (MRI) were taken into account, mPEG-SS-NH-graft-PAsp-DA@Fe3O4.Dox could be used as MRI-detectable drug carrier of Dox with enhanced cellular uptake ability.