Abstract: Microcapsules with dicyclopentadiene(DCPD) as core material and urea formaldehyde resin as wall material used for making self-healing polymer material were prepared with the in-situ polymerization method.The effect of microcapsules on the fracture toughness of epoxy resin was studied.The addition of microcapsules into epoxy resin results in the decrease of fracture toughness.When microcapsule content was kept constant,as the microcapsule size increased the fracture toughness of the epoxy resin decreased linearly and the percentage of decrease compared to the neat epoxy without microcapsules increased linearly.Moreover, the fracture toughness of the material decreases linearly with the increase of microcapsule content.