Abstract: With a ferromagnetic flow added with an additive as lubricant, the variation of friction coefficient between GCr15 (SAE 52100) steel frictional pair in a pin on disk tribometer under boundary lubrication in the presence of applied electric field was investigated. The result was discussed and the action mechanism of applied electric field on friction coefficient was analyzed. It has been found that the friction coefficient can be changed up to 35 percent with the applied direct current in different directions when ferromagnetic flow was used. The stable friction coefficient data and reversible change of friction coefficient were obtained, thus, ferromagnetic flow is of unique function on the active control of friction coefficient by externally applying electric field.