Based on the definition of physical field entropy, a temperature field entropy analysis method was proposed. Depended on researches of driving force irreversible dissipation for heat transfer, temperature field entropy quantitatively expresses the irreversible loss of system in heat transfer process. According to the study of rectangular fin efficiency, a quantitative relationship was deduced that temperature field entropy is proportional with heat conduction coefficient and thickness or it is inverse proportional with length. Compared with the curve of fin efficiency, temperature field entropy can not only reflect system's thermodynamics capability but also find out the change mechanism of fin efficiency. It is valuable for the actual application to optimize thermal system design.
