The rapid assessment method for metal fatigue performance based on the infrared thermography presents advantages such as short testing cycles, low costs, and high efficiency. However, accurately quantifying factors influencing the dissipation of energy, such as convective heat transfer and thermal radiation, proves challenging. The difficulty leads to complications in achieving the precision necessary to meet test standards in the final assessment results. A mixed-hardening constitutive model for 304 stainless steel was established and coupled with the low-cycle fatigue thermomechanical mechanism, to analyze the evolution pattern of dissipated energy caused by convective heat transfer and thermal radiation during the loading process. Furthermore, the impact of low-cycle fatigue loading frequency on the rapid assessment results of fatigue performance was explored based on the critical threshold of dissipated energy. The research indicates that during the low-cycle fatigue process of 304 stainless steel, the dissipated energy from convective heat transfer and thermal radiation constitutes over 54% of the total dissipated energy. Moreover, this proportion continuously increases with the augmentation of the convective heat transfer coefficient. Therefore, it is crucial not to neglect these factors in dissipated energy assessment calculations. With an increase in loading frequency, the peak load narrows within the region of action time. Consequently, the dissipated energy of each load cycle decreases, leading to a rapid assessment result of fatigue performance that tends to be larger than the test value.