It is difficult to find physical properties data for systems containing ionic liquids, excess molar enthalpies, binary interaction parameter, etc. In this study, the excess molar enthalpies were measured for water+ethanol+ionic liquid system using a isothermal microcalorimeter at 298.15 K. The ionic liquid used was 1-butyl 3-methyl imidazolium tetrafluoroborate, [BMIM] [BF4]. The isothermal microcalorimeter (IMC) is a flow-type calorimeter that measures the heat of mixing directly, using specific mixing cell. By employing NRTL, electrolyte-NRTL and UNIQUAC models, binary interaction parameters were determined and investigated for the correlation with vapor liquid equilibrium (VLE). The e-NRTL model with the partial dissociation was employed to correlate the ionic liquid system. The binary data of VLE system were used from literatures. Specifically, UNIQUAC volume and surface area parameters were determined using Bondi radius.