In this paper polyurethane/polystyrene IPNs was synthesized by simultaneous synthesis method.The effects of crosslinking density of one and two netWorks on the dy namic mechanical properties were reported by variation of NCO/OH ratio,30H/2OH ratio,the types of isocyanate,the molecular weight of polyethyl-glycol,(2-hydroxyethyl methacrylate and divinyl benzene,The results show that increasing crosslinking density and interpenetrating entanglement introduce“forced compatihility”, so that it accelerates curing...