Recently, various wireless applications have hugely become popular. Especially, mobile terminals such as mobile phones are actively developed. In developments of mobile terminals, miniaturization and frequency multiband of antennas are very important issues. However, there are no rational design strategy in small antenna designs. So, antenna developments depends on electromagnetic simulators or capability of engineer. And many cut-and-try processes are necessary for achieving desired characteristic. This makes many problems such as prolongation of developments. Then, now, automatic design techniques of antenna using genetic algorithm (GA) are paid attention. In this paper, the new design strategy for miniaturization of antennas is proposed by operation of chromosome-length in GA. Proposed design technique provides a minimum area necessary for keeping characteristics of a antenna. And, efficient miniaturization of a antenna and removing many undesirable conductors in a design ares are possible. Removing undesirable conductors provides lower-cost designing of antennas. The new design method can become rational design strategy for antennas miniaturization.