The molecular dynamics simulations are performed with single-crystal copper thin films under cyclic loading to investigate temperature effects on the mechanical responses. First, the method to determine the number of cycles to failure is reported: the total energy-the number of cycles curve and the stress-the number of cycles curve for nanoscale copper film are obtained; using the two curves and an additional quantitative expression, we obtain the additional quantity-the number of cycles curve, from which fatigue life of copper film is obtained. Next, under cyclic loading, with temperature rising, the number of cycles to failure of copper films increases in different manners at different temperatures: when the temperature is above about 370 K, the number of cycles to failure goes up quickly with temperature; when below about 370 K, the number of cycles rises slowly. Finally, the mechanisms of the strange temperature dependence of cyclic deformation can be explained by our developed model based on the evolutionary features of dislocation.