A study was investigated the relationship between fracture characteristics and microstructure changes according to Cu addition and heat treatment methods on the ductile cast iron. According to increment of Cu addition pearlite volume fraction was increased due to the deflect of anti-ferritizing of Cu. At the case of austempering heat treatment, fracture toughness of Cu contained specimen was decreased. The reason for the results seems to be responsible for decrement of plastic zone size at the crack tip. It was observed that the excellent fracture toughness can be obtained at the condition of normalizing and the specimen was not contained Cu. Under the such conditions, fractographs is composed of dimple pattern and fracture toughness 71.6㎫ √m, tensile strength determined as the value of 961.6㎫, respectively.