Simulating the movement, deformation and break-up of immiscible two-phase flow interface was complex and difficult in the liquid—liquid dispersion atomization system. Based on the volume of fraction (VOF) with role of surface tension and interface reconstruction, a model of tracking the immiscible liquid—liquid interface was built with two modes of large and small jet flow rates. The change of oil—water interface was tracked in the process of liquid—liquid dispersion atomization, the micro characteristics of jet break-up and drop formation and growth were simulated, and the mechanism of influence of Re, Ca and Bo criterion numbers on jet break-up and drop formation was also discussed. The results showed that the process of liquid—liquid dispersion atomization can be simulated by the interface tracking model set-up under different jet flow rates, but the simulation capability was short of tracking the process of small scale vortex break-up. Under different modes of drop formation, jet break-up was characterized by randomness, and enhanced with increase of jet flow rate; small droplets were formatted by the volatility and instability of two phases' interface. Under the modes of drop formation of trickling and laminar jet, the shape of drop, jet surface and the section of jet break-up were mainly affected by the variation of Re, Ca and Bo criterion numbers, however, for the mode of drop formation of turbulent motion jet, these criterion numbers mainly influenced the extent of jet break-up and drop size. 