Abstract: The Cu-6% Ag and Cu-24% Ag were cast and annealed or aging treated to precipitate Ag secondary particles from supersaturated Cu matrix. The interface and orientation relationship between Ag precipitates and Cu matrix were investigated. The effect of Ag precipitates on the mechanical and electrical properties of the alloys was discussed. There are a strict orientation relationship, (100)_Cu//(100)_Ag and <110>_Cu//<110>_Ag, and semi-coherence interface between Ag precipitates and Cu matrix. One dislocation exists in average nine (111)_Cu lattice intervals to adjust the lattice misfit at the interface. The strict orientation relationship and semi-coherence interface may produce significant strengthening affect and hardly increase the electron scattering in the alloys. With prolonging aging time the amount of Ag precipitates and the hardness of the alloys increase but the electrical resistivity decreases. The changes of the amount, morphology and interface structure of the precipitates should be responsible for the change of the properties during aging treatment.