The preparation and properties of luminescent polystyrene (PS) composite microspheres with rare earth (RE) organic complexes Eu(DBM)(3)(Phen) (DBM = dibenzoylmethanate, Phen = 1,10-phenanthroline) entrapped in the microspheres are presented. The luminescent composite microspheres are readily obtained by the soaking pre-existing particles method. The morphologies of resulting composite microspheres are characterized by field emission scanning electron microscope. The photoluminescence properties of the composite microspheres are also investigated. The results show that the existence of the rigid PS matrix can improve the photostability of the RE complex under UV irradiation and elongate the fluorescence lifetime of the RE complex. The improvement of the properties, the convenient preparing method, and brilliant red emission make the composite microspheres promising candidates for in cellulo applications.