In order to evaluate the fatigue effects on 304L Stainless Steel, the internal friction or damping of the material have been investigated by means of dynamic mechanical analysis (DMA), using single cantilever test modes. Before DMA measurement, the 304L plates are loaded with different cycle number and stress amplitude to simulate different fatigue condition. The amplitude dependant internal friction (ADIF) of 304L small sample is measured. It shows that the ADIF curves of DMA are associated with the pre-fatigue loading. One ADIF peak is observed near the critical strain amplitude. The DMA data of different pre-stressed samples (cyclic stress amplitude from ±80MPa to ±200MPa) show that the height of ADIF peak increases with the pre stress value. The mechanism of the peak is discussed in the paper. The results indicate that a clear correlation exists between fatigue condition and internal friction curve, so that the fatigue behaviour of 304L stainless steel can be evaluated from DMA measurements.