In this study, phase field simulation of microstructure evolution has been performed considering a two-dimensional domain size of 250µmx250µm, employing MICRESS software (A phase field solver). Microstructure evolution simulation of the cooling slope slurry generation process begins with the nucleation of primary Mg2Si particles. Seed undercooling-based nucleation model is invoked in the present 2D PF model to simulate microstructure formation, wherein experimentally determined cooling rate values are considered to simulate the slurry microstructure for different cooling slope slurry generation process conditions. The model gets activated immediately after impingement of the superheated melt over the slope free surface. Simulation findings shows that the initial growth rate of primary Mg2Si grains is high, however, it gets retarded after nucleation of α-Al grains. Spheroidal morphology of primary Mg2Si grains is observed in the cooling slope generated slurry. Whereas two different types of α-Al grains are observed from the simulated micrographs i.e., one which engulfs the evolving Mg2Si grains and the other one as independent globules. Experimental findings confirm reasonable accuracy of the developed PF model and validates its predictions of solid fraction, grain size, sphericity, grain density as well as area fraction of constituent phases.