In-phase and out-of-phase low-cycle thermal-mechanical fatigue tests were carried out on 316L austenitic stainless steel specimens controlled by computer. A nonlinear kinematic hardening model with internal variables was developed to describe the cyclic stress strain behavior of thermal-mechanical fatigue and a very good approximation of the hysteresis loops was obtained by comparing with the experiments. In order to predict the lifetime, a typical stabilized hysteresis loop of thermal-mechanical cycling was considered to be the combination of a great deal of parts at different temperatures. Each part has a different contribution rate of the energy density to the damage by introducing a damage factor depending on the temperature. With isothermal fatigue data an equivalent total strain energy density was deduced as a damage parameter and with which the calculation for thermal-mechanical fatigue lifetime prediction gave satisfactory results corresponding to test data.