Abstract: On a ball disc type friction test rig,the effects of electric states on friction force have been studied under dry friction condition for 34 kinds of friction pairs composed by Fe,Co,Ni,Ti,Cr and Cu etc alternately.The results show that under open circuit or zero current regulation state.The friction force of 10 kinds of pairs is smaller than that of these pairs under any other electric states ,especially under the zero current regulation state, under which the self generated voltage is conteracted by applied voltage,the friction force is the smallest.When the electric circuit is closed,the friction force for Ni/Cu and Ni/Fe is bigger than that of any other pairs.For any other 8 kinds of friction pairs,the friction force is almost in the same level with that under big current state.It is concluded that the electron flow between the contact surfaces can be prevented and the friction force can be decreased by applying a conteracted electric voltage to the self generated voltage of the friction pairs.And the friction forces of metallic friction pairs are influenced by self generated voltage,the compatibility of metals and their lattice structures.