The fatigue properties and the damage mechanism of a Cr-Mn austenite steel were investigated using four-point bend fatigue testing. The stress-number of cycles to failure (S-N) curve of the Cr-Mn austenite steel was measured at room temperature, at the frequency of f=20 Hz and the stress ratio of R=0.1. The fatigue strength of this Cr-Mn austenite steel was measured to be 503 MPa in the maximum stress. Multiple cracks are initiated on the sample surface after fatigue failure tests, and usually only one or two of them can lead to the final failure of the samples. Most of the cracks are initiated at the {111 }primary slip bands, especially within coarse grains. When a fatigue crack meets a new grain, it adapts to slip bands in this grain and hardly extends along the foregoing route in the previous grain. A crack is deflected at a grain boundary by crack plane twisting and tiling on the grain boundary plane, causing fracture steps on the fracture surface
