Abstract: The real contact area, plastic contact area and fraction of plastic contact area of 35CrMo specimen were calculated in two modes, i.e. deformation region after compression fatigue and worn surface in sliding against GCr15 using fractal theory. The relationships between wear and the plastic contact area, as well as the fraction of plastic contact area were analyzed. The worn morphology is observed using scanning electron microscopy. The results show that both the plastic contact area and the fraction of plastic contact area decreased as a result of delamination in contact area after sliding wear. The variation of the fraction of plastic contact area (δA_rp/A_r) can be used for variation of wear. Once the δA_rp/A_r was higher than the critical value, the wear increased sharply.