Abstract: Byproducts including cyclohexanone and cyclohexanol are formed during cyclohexene oxidation with hydrogen peroxide to produce 1,2-epoxycyclohexane. In order to obtain high purity of 1,2-epoxycyclohexane, these byproducts must be removed through rectification which needs vapor-liquid equilibrium (VLE) data of relative systems. The VLE data of the cyclohexanone-cyclohexanol binary system and the 1,2-epoxycyclohexane-cyclohexanone-cyclohexanol ternary system were studied at 101.33 kPa by an improved EC-2 VLE still. The VLE data of the ternary system were predicted by Wilson equation through fitting of the VLE experiment data of the three binary systems. The error square sum of the vapor compositions was used as the objective function to get correlation parameters. Variations between the values from the prediction, theoretical calculation and experimental data are negligible, which indicates that the experiment data are suitable for engineering design.