A three-dimensional finite element model has been developed on the anatomic basis of a crown-defected maxillacy central incisor and its casting core. According to the prepared root canal whose diameter is 1/4,1/3 and1/2 wide of the root,three core patterns are devised.Stresses data and distribution are given when the model with vertical or 45 angle incisalgingival loading,The results show that it is ofthe most suitable pattern when the diamter of the core is 1/3 wide of the root.The neck of the core and the root canal wall have more tensile and compressive stresses.The maximal stress of a model with vertical loading is less than with 45 angle incisal-gingival loading.