Uniform LaPO₄:Ce/Tb mesoporous microspheres (MMs) have been successfully prepared by a facile mass production co-precipitation process under mild reaction conditions, without using any surfactant, catalyst or further heating treatment. Then, Au nanoparticles (NPs) were conjugated to polyetherimide (PEI) modified LaPO₄:Ce/Tb MMs by electrostatic interactions. It was found that as-prepared LaPO₄:Ce/Tb@Au composite consists of well-dispersed mesoporous microspheres with high surface area and narrow pore size distribution. Upon ultraviolet (UV) excitation, LaPO₄:Ce/Tb and LaPO₄:Ce/Tb@Au MMs exhibit the characteristic green emissions of Tb³⁺ ions. In addition, the good biocompatibility and sustained doxorubicin (DOX) release properties indicate its promise as a candidate in cancer therapy. In particular, under UV irradiation, a rapid DOX release was achieved due to the photothermal effect of Au NPs derived from the overlap of the green emission of Tb³⁺ and the surface plasmon resonance (SPR) band of gold NPs at about 530 nm. The MTT assay, cellular uptaken images, the anti-tumor therapy in vivo, and the histology examination results further proved that this novel multifunctional (mesoporous, luminescent, and thermal effect) drug delivery system should be a suitable candidate for cancer therapy carriers.