Abstract: IPNs from PU(HTBN) and Polymethacrylates were synthesized by simultaneous crosslinking polymerization. The relationship between the dynamical properties of IPNs and the ratio of two components,the side groups and their contents in polymethacrylate networks were studied by means of torsional pendulum analysis.The results showed that the IPNs are semicompatible or compatible.Some more widened peaks were found in Δ-T plots of IPNs containing poly(n-BMA) and poly (iso-BMA) than of those containing poly (MMA). Acrylonitrile component was shown more affecting on the dynamic mechanical properties of IPNs obtained.