Data for two systems of isobaric vapor liquid equilibrium (VLE), n-heptane + sec-butyl acetate (SBAC) and methylcyclohexane + SBAC, were determined under atmosphere with an Ellis vapor liquid equilibrium still. The Herington method and Wisniak test were employed to determine the thermodynamic consistency of the two systems. The experimental results of n-heptane + SBAC and methylcyclohexane + SBAC were correlated by three activity coefficient models, which are the nonrandom two-liquid, universal quasichemical, and Wilson, and the correlation results fit well with experimental data. The binary interaction parameters of these models were obtained, and the results showed that these models can give good predictions. The VLE data provide theoretical basis and data support for the further study on separation of n-heptane + SBAC and methylcyclohexane + SBAC.