The Cu-Ni-Si-Mg alloy was treated by aging after varying cold deformation. The effect of cold deformation, aging temperature and aging time on the microstructure and properties of the alloy were investigated. The results indicate that the alloy produce a larger number of slip bands and dislocations after cold deformation, it can accelerate the precipitation of phase during aging, improve the microhardness and electrical conductivity. The microhardness and electrical conductivity of the alloy with 80% deformation aging at 723 K for 1h are 242HV and 35.53%IACS, respectively. The volume fraction of the precipitated phase was calculated by measuring the electrical conductivity of the alloy with 80% deformation aging at 773 K, then both the equations of phase transformation and the electrical conductivity equation were obtained.