In order to develop high quality aluminum alloy products, modeling to predict a behavior of solute distribution in dendrite and precipitation within the inter-cell region quantitatively is important. However Scheil's and Brody-Flemings's equations can't find the precipitation behavior during solidification because a diffusion in liquid phase is not considered. Numerical analysis methods typified by “Phase Field” are more effective but a calculation time has not been enough short to apply industrial use, yet. Consequentially a mathematical model is developed based on the Matsumiya's calculus of finite differences for analyzing inter-cell microsegregation and precipition. Diffusion of solutes in both the solid and liquid is taken into consideration, and realistic mesh shape to calculate microsegregation is conducted for finite difference calculation at this Matsumiya's model. But the calculus hardly predict precipitation behavior, since liquid concentration shift by precipitation during solidification is not considered. Then we improved the model to estimate precipitation of intermetallic compounds by thermodynamics database in this work. Additionally evaluation method of microsegregation used by EPMA was developed. Consequently, we built a new segregation model, which could predict both the microsegregation and the kinds and amount of intermetallic compounds.