Abstract: In the present investigation, the friction and wear characteristics of Cu-based powder metallurgy friction materials were evaluated on a space friction testing machine at high load in air. The reliability life and wear mechanisms of friction materials were investigated and revealed. The experimental results show that there were three stages in the friction process. During the first stage, the friction pair presented reliable performances, and its friction coefficient was stable. In the first stage, the abrasive wear and oxidation wear were the dominant wear mechanism.The friction properties became unstable, and the friction coefficient increased cyclically in the second stage.The dominant wear mechanism turned to be oxidation wear, accompanied by mild contact fatigue wear. In the third stage, the friction coefficient fluctuated greatly, and the dominant wear mechanism transformed to be severe fatigue wear and oxidation wear, leading to the material failure.