Fatigue cracking is one of the most common failure forms of metal structural parts in engineering practice,and the expansion of cracks leads to the dissipation of most of the plastic work in the form of heat. Therefore,an infrared thermal imaging based temperature monitoring of metal structures is one of the effective methods for assessing crack expansion. In this paper,the thermal coupling equation of the material during the crack growth is analyzed,and the direct thermal mechanical coupling simulation is carried out using ABAQUS software to reveal the effects of plastic work conversion coefficient and tensile speed on the surface temperature evolution of Q235 specimen with cracks under uniaxial tensile load. Finally,based on thermal imaging camera measurements,the correctness of this law is verified by obtaining a good agreement with the numerical simulation. The results show that the surface temperature of the specimen goes through a smooth phase and a steady increase during the tensile process. In the process of crack growth,the highest surface temperature of the specimen is located in front of the crack tip. At the same time,the higher the tensile speed,the shorter the fracture time of the specimen,the smaller the heat loss during crack extension and the higher the temperature rise on the surface of the specimen. The results are instructive for crack monitoring and early warning of metal structures.