Depending on the available experimental data (T, p, x, y, and H-E), the vapor-liquid equilibrium (VLE) data of the completely miscible isobaric systems at low pressure are accurately correlated and predicted in equilibrium phase behaviors. The VLE data of one ternary and three binary systems composed of furan, oxolane, and furan-2-carbaldehyde were obtained with a dynamic recirculating still. The three binary systems were investigated on the basis of thermodynamic theories to calculate the relationship between the vapor- or liquid-phase components and a temperature at 101.325 kPa. For comparison, the activity coefficients of the solutions were also correlated with Wilson, nonrandom two-liquid, Margules, van Laar, and universal quasichemical activity coefficient models through fitting by the least-squares method, and these models' parameters in turn were utilized to calculate vapor-phase compositions. The vapor-phase compositions computed from the measured T, p, x, and H-E based on five models showed great agreement with the experimental data. In addition, the ternary system was skillfully predicted by using the binary parameters of these models. The results demonstrate that the VLE data can be provided for the design and simulation of chemical separation processes in the biorefinery technologies and fields.