The prediction of solid-liquid equilibrium is important to describe the phase’s formation and the compositions of many chemical processes. The separation processes, which need the solid-liquid phase data, have been explored for many years, but now, with the high and new technological developments, the theoretical and practical interest in this area was increased. This work has a theoretical and computational character, whose objective is the study and application of an optimization technique for the solid-liquid equilibrium calculation. Interested of binary and ternary fatty mixtures with natural origin, this work can be applied for different profiles’ mixtures of fatty acids, triglycerides and ethyl esters using the minimization of Gibbs energy free of the systems. So, it is necessary the improvement of the thermodynamic models capable to precisely represent the equilibrium, wich was a represented by a non-linear program, and convexity analysis ensure of optimal solution found is the global optimum. The software GAMS and Microsoft Excel were used for the equilibrium problem implementation, where the description of phases was done based in known thermodynamics models. The solid phase was characterized using a modified Slaughter and Doherty model and liquid phase with Margules 2 – suffixes. In this work the on liquid phase, the Margules model assume two forms: Margules Asymmetric (MA), where the Margules parameters are different; and Margules Symmetric (MS), with equal Margules parameters, after was used Wilson Model (W) too. In this work specifically, it was calculated the equilibrium points for mixtures contain: ethyl and methyl laurate and miristate, ethyl estearate, palmitic acid and tristearin. Experimental data was used in comparative mode of binary mixtures, with good agreement between experimental and calculated points; new equilibrium dates was predicted and obtained of ternary mixtures, and the parameters model also was discovery. The results are described in form of phase diagrams for binary mixtures and surfaces of equilibrium for ternary mixtures, where the equilibrium data and the parameters model was calculated based in the square errors, that are nearly of the experimental data.