The evolution law of precipitated phase in 028 alloy was studied at different aging temperatures and for different aging time by scanning electron microscope, X-ray diffraction and hardness test. The chemical compositions, structure and hardness of the precipitated phase was analyzed, and the transformation kinetics and the growth of precipitated phase was analyzed as well. The results show that with the aging temperature increasing and the extension of time, the amount and size of precipitated phase of 028 alloy increase, and the hardness rises. Precipitate phase in grain boundaries and intragranular is mainly σ phase containing Cr, Mo, Fe and Ni elements. The transformation kinetics equation of 028 alloy at different temperatures was deduced using Avrami equation, the kinetics curve was drawn and one-dimensional growing up situation of precipitated phase was calculated, and finally the one-dimensional growth equation was obtained.