This experiment investigates the effect of aluminum powder as metallic filler of unsaturated thermosetting polyester resin on the wear rate and its mechanisms according to time. The obtained results show that the rate of wear increases with increase of time as a result of increase the temperature generated of friction in all specimens. But when we add the particles either Aluminum to polyester matrix, the rate of wear reduce as a result of increase the thermal conductivity of polyester matrix, that leads reduction of the temperature of contact surface, that leads less wear. We study the mechanisms of wear by microscope of the worn surface. It found that the predominant mechanisms of wear vary from adhesive wear at the lowest value of test time to abrasive wear (3- body) at the highest value of test time.