A novel strategy was reported in this paper to prepare polyhedral oligomeric silsesquioxanes (POSS)/polystyrene (PS) composite. Active agent was introduced to the PS chain through the treatment of acylation, reduction and reaction with sodium, and then the monofunctional POSS, which was prepared by "corner-capping" method, was chemically bonded with the modified PS chain to synthesize POSS/PS composite. The structures of all intermediates and the POSS/PS composite were characterized by FT-IR and H-1-NMR. The thermal properties were investigated by differential scanning calorimetry and thermal gravimetric analysis, with results showing that the POSS/PS composite displayed higher glass transition temperature and initial decomposition temperature than that of the parent PS homopolymer.