Microspheres with magnetic-fluorescent functions have received attention due to fluorescent tracking and target positioning. To improve the accuracy of optical imaging and the fluorescent tracking of drug release, it is essential to enhance the fluorescent intensity of microparticles. Magnetic-fluorescent bifunctional poly lactic-co-glycolic acid (PLGA) Janus microspheres [PLGA/TbLa3(Bim)12]//[PLGA/Fe3O4] with double chambers were fabricated with the double-needle electrospraying method. The fluorescent drug TbLa3(Bim)12 with dual rare earth ions was encapsulated in one chamber, while Fe3O4 magnetic nanoparticles (Fe3O4 MNPs) were simultaneously encapsulated in another chamber. In comparison, magnetic-fluorescent PLGA composite microspheres PLGA/TbLa3(Bim)12/Fe3O4 were also prepared, which encapsulated fluorescent drugs TbLa3(Bim)12 with dual rare earth (RE) ions and Fe3O4 MNPs in one chamber. The fluorescent intensity at 542 nm of Janus microspheres was about three times higher than that of composite microspheres due to a decrease in contact between fluorescent-labeling RE drug and MNPs. The fluorescent intensities of Janus microspheres with different contents of Fe3O4 MNPs and TbLa3(Bim)12 were investigated. Furthermore, the magnetic properties, thermostability, cell toxicity and hemolytic properties of Janus microspheres were also assayed to conduct a tentative exploration of their bioapplication. The Janus microspheres provide many opportunities for application in biofields such as drug delivery.