Herein, a mesoporous magnetic nanocarrier containing disulfide bonds (NH₂-SMNPs) was developed to improve the efficacy of tumor treatment and reduce side effects. After loading the carrier with doxorubicin (DOX), a nontoxic pullulan oxide was used as a gating material to form the oSMNPs/DOX nanodrug. This nanodrug exhibited uniform dispersion, good drug-loading capacity, and high saturation magnetization, enabling pH/glutathione (GSH) dual-responsive drug release in the tumor microenvironment, with a release rate as high as 81.53%. Furthermore, this nanodrug demonstrated good biocompatibility, effective capability to kill cancer cells, and competent cellular uptake ability.