Fatigue-creep interaction is the main reason for the failures of many engineering components under high temperature and cyclic loading. In this paper a new model for the life prediction of fatigue-creep interaction has been developed. In this model, the law of energy conservation and the momentum conservation principle are used to describe the process of fatigue-creep interaction. By mathematical technique, the expressions of these two rules are transformed into a simple function, which can describe the relationship between the internal energy and life. This function supposes that the internal energy change of a specimen is a constant from the initial state to the failure one under certain conditions. It should be pointed out that the new model mentioned above is applicable to the life prediction of strain-controlled tests and stress-controlled tests. Moreover, owning to its simple expression, it is very easy to use this model to predict the life of fatigue-creep interaction. To check the validity of the new model proposed in this paper, the assessments for fatigue-creep interaction tests of 1.25Cr0.5Mo steel under stress control at 540 °C have been performed. The predicted results are in a good agreement with the experimental data.