Maleic anhydride is often used as a modifier to improve the thermal performance of the material due to its unique structure and properties. However, in order to meet higher demands, it is often imperative to have better heat resistance and thermal stability. Currently, the traditional method is physically blend inorganic nanoparticles to further improve thermal performance. Unfortunately, inorganic nanoparticles have a fatal problem in that they are not uniformly dispersed in the system, which severely limits their application. Here, we used organic-inorganic molecule, MAPOSS (methyl methacrylate-based cage oligomeric silsesquioxane), to chemically modify the copolymer. And considering the unique structure of MAPOSS, we used two monomers with different polarities to study its influence on the thermal properties of the copolymerization system (MMA-MAH-MAPOSS and ST-MAH-MAPOSS), and discussed the interaction mechanism, respectively. As a result, MAPOSS introduced can not only be evenly distributed in the polymerization system via chemical bonding and physical interactions but also effectively improve the thermal stability and high-temperature resistance of the polymers. Thereinto, the Tg of MMA-MAH copolymer is increased to above 130 degrees C, and the carbon residue rate is up to 7.3%. The carbon residue rate is increased to 15.6% without affecting the Tg of the ST-MAH copolymer.