In this work, the blend of diglycidylether of bisphenol A (DGEBA) and modified polyurethane (PU) was prepared and characterized the cure behavior and mechanical interfacial properties. The N-benzylpyrazinium hexafluoroantimonate was used as a cationic initiator for cure, and the content of PU was varied within 0~20 phr. The cure behavior and mechanical interfacial properties were studied by DSC and the critical stress intensity actor (KIC) measurements. Also thermal stabilities were carried out by TMA and TGA analyses. It is found that the cure activation energy (Ea) was slightly increased on increasing the PU content, and a maximum value was noted at 10 phr PU. The mechanical interfacial properties measured from KIC showed a similar behavior with the results of conversion. These results were probably due to the increase of the hydrogen bonding between the hydroxyl groups of DGEBA and isocyanate groups in PU.