Abstract: Potassium stearate films on hydroxyl silicon substrates were prepared by dip-coating. The tribological properties of the films sliding against AISI-52100 steel ball and Si3N4 ceramic ball were investigated with dynamic static friction coefficient measurement apparatus and universal micro-tribometer in ball-on-plate configuration. The morphologies of the wear tracks of the potassium stearate films and the counterparts were examined using a scanning electron microscope equipped with an energy-dispersive X-ray analyzer attachment. The potassium stearate films on the hydroxyl-terminated substrate showed better tribological properties under relative higher sliding velocity or sliding against Si3N4 ceramic ball. Because of the different chemical nature and larger surface roughness of steel ball and Si3N4 ball, transfer film of potassium stearate is more easily formed on ceramic ball, resulting in lower friction coefficient and longer wear life as compared to that of steel ball.