In order to obtain monodisperse PLGA magnetic microspheres, compsite emulsion method and T-shaped microchannel device were adopted and used in this paper. Gelatin aqueous solution dispersed with nano-Fe3O4 particles was acted as inner aqueous phase. PLGA dichloromethane solution was served as oil phase. And PVA aqueous solution was used as outer aqueous phase. The effect of flow velocity ratio and volume ratio on the preparation of magnetic microspheres was investigated. The ingredient, morphology, size distribution and magnetic performance of resulted samples were characterized by means of FTIR, SEM and VSM respectively. Drug release performance of the microspheres was tested by using aspirin as the loading model drug. The results show that homogeneous spherical shape of the microspheres can be obtained at flow velocity ratio of the outer aqueous phase to the W/O phase is 120:1, as well as the volume ratio of the oil phase to inner aqueous phase is 2:1. The coefficient of variation (CV) with the microsphere size distribution can reach to 4.66%, indicating its good monodispersity. And the saturation magnetization is 1.52emu/g, showing high magnetic responsiveness. Meanwhile, the microsphere exhibit good paramagnetism. The drug loading microspheres show uniform release by stages within 60h. The monodisperse PLGA magnetic microspheres prepared in this paper is expected to be used for magnetic responsiveness drug carrier.