X-ray fractography is a technique to analyze the cause of the fracture from the X-ray information obtained from the irradiation on the fractured surface. The qualitative relations between the X-ray parameters and the fracture mechanics parameters has been known but quantitative relation is still under development. Through various kinds of load controlling fatigue tests, including constant effective stress intensity factor range tests, a new model for the residual stress distribution was proposed. The quntitative relation between the X-ray and fracture mechanics parameters can be obtaind from this model.