In this paper, equilibrium phase diagram in Al-15Si-xCu system piston alloys was calculated using “Pandat” software. The influence of Cu content on the friction and wear behavior of Al-15Si piston alloys at elevated temperature was investigated by the combination use of optical microscopy (OM) and scanning electron microscopy (SEM). Experimental results showed that the abrasive and wear weight and the friction factor in the T6-treated piston alloys were reduced with the increase of Cu content. The friction and wear properties differ slightly in the piston alloys containing 4.5% and 5.5%Cu, which is related to the high thermally stable precipitates, i.e., Q-phase, ε-phase, and θ-phase. For the piston alloys containing low Cu content, the wear mechanism belongs to adhesive wear, while abrasive particle wear is responsible for the high Cu content piston alloys.