Abstract: The influence of metal electrode potential on the friction coefficient of ceramic/metal sliding couple was investigated with a tribotest developed in our laboratory. It was observed that the friction behavior varied with the electrode potential, especially in a potential range of -1.0 V~-1.4 V, the friction coefficient was controllable to some extent. The observation of the worn brass surafce morphologies with a scanning electron microscope showed that the worn surafce under the potential of -1.0 V~-1.4 V was similar to that under the open current potential. Electrochemical method has been applied to analyze the test results. It was showed that the controlability of the friction was dependent on the electrochemical process of the frictional pair in the presence of the electric potential. However, further work is needed to disclose the essence of such a dependence.