In this study, a electrical pitting tester and SEM are employed to investigate the effects of supply voltage, supply current, and oil film thickness on the electrical behavior, the action forces, and the formation mechanism of electric pitting for the lubricated surface of steel pair at sliding speed of 1£gm/sec using an additive of MoS2 in paraffin base oil under DC electric field. According to the experimental results and the observations of the surface pitting, two electrical pitting regimes are found under the influences of shaft voltage, oil film thickness, and particle concentration of additive, namely, pitting and no- pitting regimes in static condition. The area of pitting regime increases with increasing additive concentration and supply current. Furthermore, The ratio of pitting area to the interface power increases rapidly with increasing additive concentration and oil film thickness. This results from the molten plateau that directly connects two specimens, and the interface power is mainly consumed at the heating of the plateau and the interfacial materials. However, the weld strength of the plateau isn¡¦t influenced with additive concentration. It is known from the observations of the surface pitting in dynamic pitting occurs that the pitting width increases with increasing oil film thickness and additive concentration. Finally, the formation processes of electric pitting on the lubricated surface for both static and sliding conditions are deduced from the results of the normal force, the friction force, the interface impedance and the observations of the surface pitting.