The thermal and mechanical properties，microscopic morphology and crosslinking density of bisphenol A modified epoxy resin and CTBN toughened epoxy resin have been examined．Four different curing agents，namely，piperidine，triethanol amine，70# anhydride and boron trifluoride．ethylamine complex have been used．The tremendous influence on the toughening effect by the added bisphenol A was only obtained when the basic catalytic curing agents such as piperidine and triethanol amine were used．The rise in the impact toughness of the cured material is ascribed to the decreased crosslinking density of the epoxy resin network．The rise of the fracture toughness is the synegistie effect of the ineressed volume percent of the rubber phase and the dec-teased erosslinking density of the matrix．CTBN is abbreviated from earboxyl terminated butadieneacrylOnitrile rubber．70# anhydride is a eutectic mixture of four tetrahydrophthalic anhydride isomers．