Irradiation-induced generation of point defects accelerates the evolution of the microstructure of nuclear power plant materials and affects the reactor lifetime to a large extent. In this paper, based on the quadratic continuous phase field model of the phase field method with coupled vacancy and interstitial atoms, the phase separation of Fe-15at.%Cu-1at.%Ni-1at.%Mn alloy under the vacancy diffusion mechanism is simulated using this model, and the interaction mechanism between the vacancy diffusion-induced point defects and the Cu-rich phase is investigated. The results show that the presence of vacancy and interstitial atoms promotes the growth and coarsening of the Cu-rich phase, the increase of the initial concentration of point defects promotes the phase separation and accelerates the nucleation rate of the precipitated phase, and the elevated temperature delays the growth and coarsening of Cu atoms and vacancy rings, and the point defects can also increase the yield strength to a certain extent, which provides a new idea to investigate the effect of vacancy diffusion mechanism on the properties of irradiation-resistant materials.