The effects of Ni addition on the liquid phase separation and giant magnetoresi stance (GMR) of Cu Co alloys were discussed. The results reveal that Ni additio n can partially restrain the liquid phase separation of Cu Co alloys, resultin g in a decrease of volume fraction for the Co rich particles separated from the liquid phase and in refined microstructures. The composition analyses indicate t hat Ni is dissolved in both the Co rich and the Cu rich phases, but Ni content in the Co rich phase is much higher than that in the Cu matrix. At the same ti me, Ni addition enhance the solubility between Cu and Co, especially Cu in Co s olid solution. Ni alloying into Cu Co alloys can fully prevent the liquid phase separation during melt spinning, which is very beneficial to improve GMR of Cu Co alloys. The effects of Ni addition on the liquid phase separation and giant magnetoresistance (GMR) of Cu Co alloys were discussed. The results reveal that Ni additio n can partially restrain the liquid phase separation of Cu Co alloys, result in g in a decrease of volume fraction for the Co rich particles separated from the liquid phase and in refined microstructures. The composition analyzes t hat Ni is dissolved in both the Co rich and the Cu rich phases, but Ni content in the Co rich phase is much higher than that in The Cu matrix. At the same ti me, Ni addition enhance the solubility between Cu and Co, especially Cu in Co s olid solution. Ni alloying into Cu Co alloys can fully prevent the liquid phase separation during melt spinning, which is very beneficial to improve GMR of Cu Co alloys.