Abstract This work is devoted to analysis of thermodynamics properties of the fatigue cracks propagation in metals. A theoretical description of the elastoplastic condition at the fatigue crack tip is proposed on the base of an elastic solution and a secant elastic modulus. An experimental confirmation of the theoretical approach to the heat flux calculation at the fatigue crack tip is carried out. The character of heat dissipation at different stages of crack propagation is studied. The investigation of the fatigue crack propagation was carried out on flat samples with stress concentrator made from stainless steel AISE 304. The stress concentrator was the side notch. Infrared thermography method and the contact heat flux sensor based on the Seebeck effect are used to monitor the dissipated thermal energy. The stress intensity factor was constant during the loading. The plastic zone shape under monotonic uniaxial loading was calculated theoretically.