Seven kinds of poly(methyl methacrylate) (PMMA) films doped with [60]fullerene or its inclusion complex of p-tert-butylcalix[8]arene were prepared and characterized by FTIR, UV-vis, TG, and DSC. It was found that the thermal stability of PMMA is much improved by doping with the inclusion complex in comparison with [60]fullerene itself, that is, the inclusion complex retards the thermal depolymerization of PMMA very effectively. The influence of incorporating active carbon powder or calix[8]arene on the thermal stability of PMMA was also investigated.