**Abstract:**
Vapor- liquid equilibrium data for three strongly associated binary systems was taken for estimation of parameters of four different thermodynamic models by developing a general code using optimization techniques in MATLAB software. Isobaric vapor-liquid equilibrium measurements are considered in this work for three binary systems methanol-ethanoic acid, methanol-water and water-ethanoic acid at 101.325 kpa. None of the systems form an azeotrope. The activity coefficient has been calculated taking into consideration the non-ideality of the mixture. The experimental T, x, y data are used to estimate nonrandom two-liquid (NRTL), Wilson, Margules and VanLaar model parameters, and these parameters in turn are used to calculate vapor phase compositions. The activity coefficients of the solution were correlated with NRTL, Wilson, Margules, and VanLaar models through fitting by least-squares method. The VLE data of binary system were well predicted from these binary interaction parameters of NRTL, Wilson, Margules, and VanLaar model parameters without any additional adjustment to build the thermodynamic model of VLE for binary system and obtain the vapor-pressure compositions and the calculated bubble points.

**Keywords:**
Binary mixture, Vapor liquid equilibrium, Wilson, Margules, VanLaar, NRTL.