Abstract: Dicyclopentadiene cyanate (DCPDCE) was chemically modified by a novel phosphoruscontaining polyhedral oligomeric silsesquioxane (P-POSS). Curing kinetics of DCPDCE/P-POSS composite system and pure DCPDCE were studied by a nonisothermal differential scanning calorimetry method, and chemical structures of POSS/DCPDCE composite system at different curing stages were monitored by Fouriertransform infrared spectroscopy. The results indicated that both DCPDCE/P-POSS composite and pure DCPDCE could be completely cured by a programmed temperature method. In addition, hydroxyl groups in P-POSS enhanced curing reaction of DCPDCE and thus improved curing degree of the composite system.