An exergy balance equation which relates to heat and mass transfer on distillation stages was derived from the theory of non-equilibrium thermodynamics. This equation was used to analyze an ethylene distillation column, and the result checked satisfactorily with that of equilibrium thermodynamic exergy analysis.In a multiphase discontinuous system, each phase may be considered as a subsystem, and all subsystems are separated by interfaces. With appropriate hypotheses, the equation of exergy loss relating to energy and mass transfer through interfaces may be expressed as follows:D=T_o[J_q·Δ(1/T)-sum from k to n J_k·Δ(μ_k/T)] Thus, profound insight into distillation process could be gained to provide ideas for further improvement of the distillation scheme. An exergy balance equation which relates to heat and mass transfer on distillation stages was derived from the theory of non-equilibrium thermodynamics. This equation was used to analyze an ethylene distillation column, and the result checked satisfactorily with that of equilibrium thermodynamic exergy analysis. With appropriate phase hypotheses, the equation of exergy loss relating to energy and mass transfer through interfaces may be expressed as follows: D = T_o [J_q · Δ (1 / T) -sum from k to n J_k · Δ (μ_k / T)] Thus, profound insight into the distillation process could be gained to provide ideas for further improvement of the distillation scheme.