With the Uddeholm self-restricted thermal fatigue method, the transformation of phase constitutions and morphology of boride layer after 3000 cycles of thermal fatigue test was studied by XRD and SEM and the surface residual stress in the process of thermal fatigue test was researched by X-ray Stress Analyzer; the formation of the heat checking of boride layer was also analyzed. The results show that with the high strength and excellent thermal stability of boride layer, morphology of heat checking alters. Therefore, boronizing treatment of H13 steel improves its thermal fatigue behavior.