The P (MMA-co-St) copolymer containing dysprosium was prepared by the in-situ polymerization of a gel, which was obtained by doping directly dysprosium tri-isopropoxide in the monomer mixtures of methyl methacrylate and styrene (monomer mole ratio was 1:1). The effect of dysprosium tri-isopropoxide on the properties of P (MMA-co-St) copolymer was also studied. It was shown that the linear structure of P (MMA-co-St) containing dysprosium changed into a crosslinked network with increasing dysprosium content, resulting in improvement of properties, such as resistance to heat and solvent, storage modulus and fluorescence strength. Moreover the copolymer is a material with high uniformly distributed rare earth content and improved transparency.