Terbium rare earth complex has been synthesized with dibenzoylmethane(DBM) as the first ligand, 1,10 -phenanthroline(phen) as the second ligand and was characterized by means of IR spectrum, 1HNMR, elemental analysis and MS spectra. The polymer composites has been prepared by addition terbium rare earth complex to polymerization system of MMA-St under certain conditions and was analysed by UV-Vis spectrum , fluorescence spectra and thermogravimetry(TG). The results showed that the material has the higher decomposition temperature ( 220 ℃ ), the stronger UV absorption in 350nm and 262nm. The fluorescence spectra of the material shows characteristic absorption peaks of Tb3+. Research indicates that the polymer composites has the higher thermal stability and the stronger UV absorption. The flame retardant experiment indicated the average degree of carbonation is 9. 7cm which suggests the polymer composites has better flameproofing.