The Fe3O4@mSiO2 nanocarrier that consisted of a magnetic Fe3O4 nanoparticle core and a mesoporous silica (mSiO2) shell was synthesized. It shows a uniform sphere morphology about 65 nm in diameter. Considering the magnetic hyperthermia of Fe3O4 under an alternating magnetic field (AMF), a thermosensitive polymer, poly[(ethylene glycol)-co-(L-lactide)] (P(EO-co-LLA)), was used as “gatekeeper” coating outside Fe3O4@mSiO2 to regulate the drug release behavior. The design of the nanocarrier was expected to block off the pores at low temperature and to reopen them at high temperature reversibly. The obtained hybrid nanocomposites were capable of loading the anti-cancer drug doxorubicin (DOX) and controlled drug release behavior trigged by the hyperthermia of Fe3O4 under AMF. Besides, the nanocarriers also show pH-sensitive drug release based on the slight differences between the tumor (weakly acid) and the normal tissue (weakly alkaline). What’s more, the chemotherapy of DOX combined with magnetic hyperthermia can improve the cytotoxicity obviously. On the basis of the high stability and excellent controlled release performance, the multifunctional nanocarriers exhibit potential applications in targeted-control drug release and hyperthermia for cancer treatment.