A steady-state optimization for the fractionation unit of an industrial benzene-toluene-xylene (BTX) plant was developed. Because the fractionation unit of the BTX plant has narrow ranges of boiling point and doesn’t have any sidecut and side reboiler, we employed the boiling point estimation method in the modeling and simulation of the unit. The well-known Soave-Redlich-Kwong state equation was employed to compute required thermodynamic properties. The results of simulations showed very good agreement with the actual operation data. The objective of the optimization was to maximize profit of fractionation unit. The successive quadratic programming algorithm was utilized and objective functions for each fractionation column were set up based on utility and operation costs and selling prices of products. The graphical user interface of the optimization system was developed to provide convenience and flexibility in actual applications.