Abstract: For the highest azeotrope system formed by ethylenediamine and water, it is difficult to effectively separate by conventional distillation methods. Pressure-swing distillation is a special distillation method that completes azeotrope separation based on the characteristic that the azeotrope point changes obviously with pressure. In order to obtain the thermodynamic model and parameters required for pressure-swing distillation calculation, the vapor-liquid equilibrium data of ethylenediamine-water binary system at 30 kPa were measured by Rose vapor-liquid equilibrium kettle, and the thermodynamic consistency of the experimental data was tested by Herington area integration method. On this basis, UNIQUAC and NRTL activity coefficient models were used to correlate the experimental data of vapor-liquid phase, and the interaction parameters of binary system and the deviation between experimental values and predicted values under the two models were obtained by regression. The results show that the average absolute deviations of NRTL and UNIQUAC activity coefficient models are 0.028 05 and 0.030 78, respectively, and both models can well correlate the phase equilibrium data of ethylenediamine-water system. In contrast, the NRTL model is more consistent with the data of ethylenediamine-water vapor liquid equilibrium at low pressure, and is more suitable for simulating the separation process of ethylenediamine-water system at low pressure.