Abstract: Low cycle fatigue tests were carried out on a number of fatigue specimens of 19Mn6 steel. Multiple small cracks initiated on the surface and their propagation were observed by optical metallography. A parameter,DW, is proposed for quantitative description of local fatigue damages based on local damage concept.DWincreases exponentially with the number of recycles until reaching the critical value, 1. The nonlinear damage factor,m, obtained by correlation of the experimental data is smaller than that by macro-measurement.