Abstract: The friction performace and the characteristics of adhesion damage of the wet Cu-based friction materials were studied through test bench for clutch sketch. The surface morphology and the element of the damaged surface were analyzed by scanning electron microscope and energy dispersive spectrdmeter, respectively. The results show that friction material suffered adhesion damage when power density was higher than the critical value.There are a lot of the spalling pits with lengths of 200 μm to 1 mm on the surface in the early stage of adhesion damage. There were a lot of continuously distributed punctate tearing pits in the middle stage of adhesion damage. The copper transferred from Cu-based friction materials to steel disc in case of severe adhesion damage, which led to the abnormal to torque curve. When power density was lower than the critical value, the variation of friction performance of the friction materials was insignificant before adhesion failure.