This study verified the relationship between fracture mechanics parameters(${Delta}K,;K_{max}$) and X-ray parameters ($(sigma}_r,;B$) for G365 steel at elevated temperature up to $300{circ}C$. The fatigue crack propagation test were carried out and X-ray diffraction technique according to crack length direction was applied to fatigue fractured surface. The residual stress on the fracture surface was found to increase in low ${Delta}K$ region, reach to a maximum value at a certain value of $K_{max}$ or ${Delta}K$ and then decrease. Residual stress was independent on stress ratio by arrangement of ${Delta}K$ and half value breadth was independent by the arrangement of $K_{max}$. The equation of ${sigma}_r-{Delta}K$ was established by the experimental data. Therefore, fracture mechanics parameters could be estimated by the measurement of X-ray parameters.