Abstract: In the process of microemulsion flooding, microemulsion phase state may be affected by the adsorption of core and the distribution of oil and water, and the upper phase, the middle phase or the lower phase microemulsion will appear. Accurate description of microemulsion phase state and quantitative discrimination of equilibrium phase composition are of great theoretical value and research significance for the design of microemulsion flooding system and improving the recovery efficiency of microemulsion. Therefore, in this paper, microemulsion phase model is deeply studied. Aiming at the difficulty of solving the existing Hand model and the unknown parameters of the improved HLD-NAC model, we introduce the binodal curve range parameter D and the asymmetric migration degree parameter B, and establish a new phase behavior description method of the binodal curve, the two-phase plait point lines and the III-phase node line. Then the phase discrimination programming of microemulsion was carried out, and the change laws of phase number, phase type and mass fraction of equilibrium phases of any microemulsion system under different salinity were revealed. The results show that the simulation results of microemulsions accord with the salinity scanning law, and can accurately identify the complex microemulsion phase states.