Abstract: Two epoxy resin systems （139S and BE188EL cured with hexahydrophthalic anhydride） were modified with 3glycidoxypropyl polyhedral oligomeric silsesquioxane cage (POSS) led to POSS/epoxy hybrid materials. The impact strengths of the two epoxy systems were increased by 57.45 % and 32.26 %, the flexural strength were increased by 9.23 % and 5.07 %，and the thermal residual weight increased by 50.19% and 20.16%. Meanwhile, the coefficients of thermal expansion was lowered.

Key words: epoxy resin, polyhedral oligomeric silsequioxane, mechanical properties, thermal stability, coefficient of thermal expansion