A new separation method, complex extractive distillation, was put forward in this work for separating acetic acid and water. Tributylamine was selected as the separating agent. The reversible chemical interaction between acetic acid and tributylamine was verified through infrared spectra (IR) and mass chromatogram (MS) technique. The mathematics models of equilibrium (EQ) stage with and without incorporating chemical equilibrium equations were, respectively, established to simulate the extractive distillation column. From the comparison of simulated results with experimentally observed results, it was concluded that the EQ stage model was accurate whether chemical equilibrium equation was incorporated or not because the chemical equilibrium constant was small under the operation condition. (C) 2003 Elsevier B.V. All rights reserved.