In this study, the fracture criterion of the conventional modified stress fracture strain model for the notch defect was changed from the mean value of the triaxial stress of the tensile specimen to the maximum value and evaluated by the fracture mechanics method. Finite element analysis was performed using ductile fracture simulation technique with varying notch radius based on SM490A experimental data. The fracture toughness of the notched specimen was lower than that of the experimental specimen when the fracture criterion using the average value of the triaxial stress of the conventional tensile specimen deepest point was used. The crack initiation fracture toughness was predicted when the maximum torsional stress was used as the fracture criterion. These results show that it is reasonable to use modified fracture criteria to determine fracture toughness for notch defects.