A facile method is developed for the fabrication of magnetic iron oxide nanoparticle-hollow mesoporous silica spheres (IONP-HMSs) and explored their potential application in drug delivery. Through the self-assembling process of IONPs and the formation of mesoporous silica shells, the IONP-HMSs with hollow interior cavity were obtained. The cetyltrimethyl ammonium bromide (CTAB) encapsulated IONP-containing spheres served as the template to establish the mesoporous silica shells. Typical anti-cancer drug, doxorubicin hydrochloride (DOX) was applied for drug loading and release process of IONP-HMSs, which demonstrated the IONP-HMSs have a high drug loading efficiency and allow pH-trigged release of DOX in vitro. Moreover, the IONP-HMSs exhibited excellent biocompatibility and enhanced DOX therapeutic efficacy to HeLa cells. Compared with traditional methods, the reported microemulsion-based method for the synthesis of IONP-HMSs enables the formation of hollow-structured nanocomposite without any complex template-removing process, which could pave the way to improving the therapeutic efficacy in drug delivery system.