The liquid holdup of ebulliometer used in this research was determined to be 1.56 ml. The vapor-liquid equilibrium data of methanol-ethanol system are measured by the ebulliometer to confirm the reliability of the apparatus used. The vapor-liquid equilibrium data of trans-2-butenal-paraldehyde at 110.3kPa was obtained by ebulliometric measurement. The data of the saturated vapor pressure-temperature dependence of trans-2-butenal and paraldeyhyde were measured and correlated by Antoine equation.