A simulation model for catalytic reforming has been developed to monitor commercial plant performance. The model consists of various modules to predict temperature and concentration profiles, catalyst deactivation and cycle length, inter stage heater duties, recycle gas composition and octane number. The lumping details of the feed and reaction scheme, parameter estimation and model validation details are given. The model numerically integrates the component and energy balance equations for the combined feed and recycle gas in each reactor and then simulates flash separator for recycle gas composition. The results of the model validated for four different commercial reactors performance are presented.