Abstract: The solid-solution treated and aged Cu-Cr alloy were welded by friction stir welding respectively, and the microstructure and mechanical properties of welded joints were studied by hard test, electrical conductivity test, optical microscopy and scanning electron microscopy. The results show that the difference of microstructure between different zones in welded joint of friction stir welding for Cu-Cr alloy was distinct. The hardness value of weld nugget zone, 78 HB, in the joint of solid-solution treated alloy was highest, the farther to the welded seam center, the lower of the hardness and the electrical conductivity. The hardness value of HAZ, 91 HB, in the joint of aged alloy was lowest, and the electrical conductivity dropped gradually from matrix to welded nugget zone.