Effect of Cr contents(Cr: 0.27, 0.45 and 0.65wt.%) on precipitation process has been studied by electrical resistivity measurements, hardness and scanning electron microscope. The first stage of the process consists of the formation of Cr-rich particles, the second stage consists of the competitive growth of these particles. The kinetics of precipitation could be described by Johnson-Mehl-Avrami equation, $f(t)=1-exp(-kt^n)$. The values of n were found to be in the range from 0.17 to 0.39 at the first stage and from 1.0 to 1.5 at the second stage. The activation energies of Cu-Cr alloys were determined by Cross-Cut method and were 90~136 kJ/mol. The maximum hardness value of $H_RB$ 84 was obtained in Cu-0.65wt.%Cr alloy.