A tailless aircraft is an attractive design concept due to its aerodynamic efficiency. However, the tailless aircraft has disadvantages in static stability compared to conventional aircrafts. To obtain comprehensive design guidelines for tailless aircrafts, which satisfy aerodynamic efficiency as well as static stability, this study investigates the influences of tailless aircraft design parameters on static stability and aerodynamic performance. To accomplish this object, the tailless aircraft is further optimized for aerodynamic and static stability performance using optimization techniques and computational fluid dynamics (CFD) to evaluate aerodynamic coefficients and derivatives related to static stability and the Dutch roll mode. As the first step of optimization, the optimal design problem is determined and CFD is performed for various tailless aircrafts with different design parameters to investigate whether a tailless aircraft which satisfies requirements of static stability exists in design space we set. The results are then studied to reveal the trade-offs and relationships between static stability, aerodynamic performance, and design variables. Trade-offs are confirmed between the derivatives related to the Dutch roll mode and aerodynamic performance. The derivatives related to rolling and yawing static stability are also trading-offs. The trend is revealed that when improving yawing static stability, the derivatives related to Dutch roll mode also alleviate. In addition, the relationship between the derivatives related to static stability, aerodynamic performance and different parameters of the shape was revealed. The trends indicate that a lower washout angle leads to higher aerodynamic performance while a higher washout angle is more effective for alleviating the Dutch roll mode. The results of the optimization reveal the characteristics of configurations which satisfy all of the static stability requirements. These configurations have relatively high sweepback angle and dihedral angle. In addition, the washout angle and the sweepback angle are key to satisfying yawing static stability. Furthermore, the dihedral angle contributes rolling stability. It is also revealed that within the configurations which satisfy all of the static stability criteria, washout angle and magnitude of the maximum camber are dominant design parameters for aerodynamic performance. In addition, dihedral is also dominant design parameter for the derivative related to the Dutch roll mode.