Rigid PUF (polyurethane foam) is one of materials for in-ground LNG storage tanks which have been successfully constructed since 1970. For LNG carriers, however, it is necessary to use a material having sufficient strength to withstand cyclic load and impact load caused by hull motion in waves and hull deformation etc., and having excellent resistance to crack propagation as well. To meet this requirement, reinforced PUF consisting of continuous glassfiber uniformly dispersed in rigid PUF has been developed especially for TGZ Mark III cargo containment system. The present paper aims at making a quantitative evaluation of the reinforcing effect of glassfiber in reinforced PUF from a viewpoint of increased crack resistance performance. In this report, crack extension behavior and fracture toughness of reinforced PUF have been examined in detail in comparison with those of rigid PUF under a three-point bending test on notched beam specimens at room temperature. Acoustic emission analyses and finite element simulations have been shown to be successful in comparing the fracture behavior of reinforced PUF with that of rigid PUF.