In order to investigatet he fractal behavior of the local time series curves about the friction coefficient of the contact surface of scroll compressor endface friction at the initial running stage and stable wear stage under the oil lubrication condition,two friction and wear tests were performed on the TRB multifunctional friction and wear tester respectively with different materials such as the nodular cast iron and the copper alloy,the nodular cast iron and the aluminum alloy,all of which had different surface roughness.The time series signal curves of friction coefficient during the running process was collected and fractalized.The results show that the time series curves of friction coefficient had obvious fractal characteristic and the complexity of the runningin process can be judged according to the fractal dimension of the friction coefficient time series signal in the friction process.The greater surface roughness of the friction pairs during the oil lubrication,the greater the average friction coefficient,but the smaller the fractal dimension of the friction coefficient curves,and the more the irregular fluctuation of the fractal dimension of the local time series curves of the initial friction coefficient.The change of the soft material surface roughness has the greater effect on the friction coefficient and partial fractal dimension.