A modefied Newton-Raphson method is presented in this report. It consists of introducing relaxation factor ω

parameter α into general Newton-Raphson method. In convergence process

physical variables are updated reasonably in physically meaningful range

so they smoothlly converge to a solution. Examinations were made with nonideal distillation system. The results showed that the present method gave better convergence character than either Newton-Raphson or successive substitution approach.