The kinetic model for a ternary system is introduced based on the microscopic diffusion form of the phase field equations for a binary alloy. The equation is solved in the reciprocal space. This model is used to investigate the early precipitation process of Ni 75 Al 10 V 15 by simulating the atomic pictures of the two ordered phases and calculating the order parameters of γ ′(Ni 3Al) phase. Simulation results show that the γ ′ ordered phases precipitate from the disordered matrix by a non classical nucleation mechanism, and the nonstoichiometric γ ′ ordered phase appears first and then transforms into the stoichiometric one. Clusters of V atoms appear at the γ ′ phase boundaries followed by the formation of the nonstoichiometric θ ordered phase. The farther the location from γ ′ phase boundary is, the lower the order degree of θ phase is. There exist two kinds of DO 22 ordered domains: a horizontal one and a vertical one, related to their adjacent γ ′ phase boundaries. The model could describe the atomic ordering and composition clustering simultaneously, and any a priori assumption about the new phase structure and precipitation mechanism etc. is unnecessary. The kinetic model for a ternary system is introduced based on the microscopic diffusion form of the phase field equations for a binary alloy. The equation is solved in the reciprocal space. This model is used to investigate the early precipitation process of Ni 75 Al 10 V 15 by simulating the atomic pictures of the two ordered phases and calculating the order parameters of γ ’(Ni 3Al) phase. Simulation results show that the γ’ ordered phases precipitate from the disordered matrix by a non classical nucleation mechanism, and the nonstoichiometric γ ’Ordered phase appears first and then transforms into the stoichiometric one. Clusters of V atoms appear at the γ’ phase boundaries followed by the formation of the nonstoichiometric θ ordered phase. The farther the location from γ ’phase boundary is, the lower the order degree of θ phase is. There exist two kinds of DO 22 ordered domains: a horizontal and vertical one, related to their adjacent γ ’phase boundaries. The model could describe the atomic ordering and composition clustering simultaneously, and any a priori assumption about the new phase structure and precipitation mechanism etc. is unnecessary.