The effects of aging temperature and aging time on properties of Cu-2.1Ni-0.5Si -0.2Zr-0.05Cr (wt.%) alloy were studied. The transformation ratio of new phase in Cu-2.1Ni-0.5Si-0.2Zr-0.05Cr alloy was calculated when aging at 400°C, 450°C and 500°C by measuring electrical conductivity, the relation between the electrical conductivity and the quantity of new phase. The Avrami-equation of phase transformation kinetics and the Avrami-equation of electrical conductivity during aging were established for Cu-2.1Ni-0.5Si-0.2Zr-0.05Cr alloy, on the basis of linear relationship between the electric conductivity and the volume fraction of precipitates. The calculated values of electrical conductivity well consistent with those of experiment can provide reference on the alloy of production process. The characteristics of precipitates in the alloy after solution treatment and cold rolling were established, and the results show the precipitate was δ-Ni2Si phase.