Epoxy network polymers are widely used in structural materials, adhesives, paints, and electronics materials. Several modifiers, such as rubbers, fillers, and thermoplastic polymers, were blended to improve the fracture toughness of the cured epoxy polymers, as well as the investigation of new chemical structures of epoxy oligomers and curing agents. Recently, block copolymers having self-assembly ability get attracted attention as modifiers for the toughening of epoxy resins. In this paper, the self-assembly nano-structures of the epoxy polymer blends and the toughening effect are reviewed.