Abstract: In order to investigate the fractal behavior of friction signal and the change regularity of its fractal dimension with sliding velocity and contact load,friction and wear tests of pin(GCr15 steel)-on-disc(C45 steel) were carried out on an MMW-1 type wear tester.Friction coefficient signal data were collected during the initial 1000 m relative sliding distance under various normal contact loads and sliding velocities.The fractal behaviors of the friction signals were studied and the fractal dimensions were calculated using the method of structure function measurement.Results show that the friction coefficient signals had obvious fractal characteristics and their fractal dimensions were changed with the variation of load and velocity.Under the same load the value of fractal dimension increased with the increase of sliding velocity,and under the same velocity the value of fractal dimension increased with the increase of contact load.In addition,there was a direct ratio between the fractal dimension of friction coefficient and the wear rate of material.