This paper presents the synthesis of full-interpenetrating polymer networks (full-IPNs) based on blocked polyurethane (PU)/vinyl ester (VE). The IPNs were prepared from a blocked NCO-tenninated PU prepolymer with a chain extender and a VE prepolymer with an initiator using simultaneous polymerization (SINs) method. From LR spectrum analysis, it was found that the major reactions in the blocked PU/VE IPNs system are the self-polymenization of the blocked PU/chain extender and the self-polymerization of the VE/initiator. The swelling ratio of the IPNs increased with an increasing blocked PU content, and decreased with an increasing filler and VE initiator content. The density decreased with an increasing blocked PU content, and increased with an increasing filler and VE initiator content. The weight loss by thermogravimetric analysis decreased with an increasing VE and filler content. It was confirmed from scanning electron micrography that the system was heterogeneous and more than one phase existed in the IPNs.