Abstract: High temperature (700, 800, 900 K)tensile creep behavior and creep mechanism of Cu-0.2Zr alloy and Cu-3Ag-0.5Zr alloy were studied. The results indicate that the creep resistance of Cu-Zr alloy was better than that of Cu-Ag-Zr alloy. At temperature of 700 K, viscous dislocation slip was the creep process control mechanism of two alloys. At temperature of 800 K, the creep process of two alloys was mainly controlled by grain boundary diffusion mechanism. High temperature creep fracture of two alloys showed ductile intergranular fracture with secondary cracks, there were many cacities on the fracture of the Cu-Zr alloy. Creep rupture data of two alloys corresponded with the Monkman-Grant relationship.