Precipitation behavior of the early aging stage and the transformation kinetics were studied by analysing the electrical resistance variation of the solution Cu-Ni-Si alloy in the process of aging. Due to the linear relationship between electrical conductivity and volume fraction of precipitates, the transformation kinetics equation can be educed from the Avrami empirical formula, on the basis of this equation, transformation kinetics curve and "C" curve of the isothermal transformation were established.