The influence of direct current field (DCF) on powder-pack boriding has been investigated by applying DCF between boriding agent and specimen during the soaking. Experimental results show that DCF has the function of heating the agent and the specimen and thus enhancing boriding. It is shown that the specimen’s side facing anode has the deepest boride case when the specimen is taken as cathode. It is proposed that DCF forces active boron-containing species to diffuse toward the specimen at the cathode. This makes boron concentration around the specimen as cathode higher than that at the anode or other position and that in the conventional powder-pack boriding (CPB), which relatively decreases boron’s absorption by inner wall surface of the pack box and the non-working surface of the specimen. DCF’s physical effect of enhancing chemical reaction in the agent increases the activity and concentration of active boron atoms and boron-containing species, which overcomes the shortcoming that CPB can not produce enough boron-containing species by conventional way of heating.