The backmixing characteristics of the liquid in a countercurrent two-phase flow catalytic distillation column was examined. The residence time distribution (RTD) curves were interpreted using the axial dispersion model. The axial Peclet number was obtained by the least-squares fitting method in the entire time domain, and the correlation, Pe a = 10.487 Re L – 0.224 Re G – 0.0765 , was obtained. An example is given to show the effect of axial dispersion on the yield of Methyl Tert-Butyl Ether (MTBE) synthesized using catalytic distillation.