With the development of numerical technique and computer technology, the numerical modeling of the solidification process is changing from macro to micro modeling. By micro modeling not only the solidified microstructure of materials can be predicted, but also the accurate information of latent heat releasing can be provided for the macro modeling. The complete coupling of macro and micro modeling can result in a more accurate prediction for the solidification process of casting alloys. In the paper the state of art of the microstructure simulation was given in order to describe the main methods of micro modeling, such as deterministic, stochastic and phase field modeling, etc. Because of the complexity of numerical simulation of the solidification microstructure, it is necessary to study deeply the microstructure simulation, which would be the important research orientation in the field of computational materials science. Finally, the existent problem and the future developing orientation were analyzed.