This study describes a computer aided design system on involute gear for power transmittion. Input data for gear design are pressure angle 20˚, transmitted power, gear volume, gear ratio, addendum ratio of rack, dedendum ratio of rack, edge radius of rack, allowable contact stress and allowable bending stress etc, Bending strength contact strength and scoring are considered as the design constraints. Method of optimization developed this study. The developed gear design system can design the optimized gear that minimize the number of pinion teeth with face tooth.