Abstract: According to the design requirements related to high endurance factor, short take-off and landing, deforming resistance of MALE UAV, the investigation of the design methodology on multi-constraints two-element airfoil is conducted based upon the earlier studies on the one-element airfoil. In this paper, the geometry of the two-element airfoil is generated with the method of controllable conic curves accompanied with the control points, and the parameters of control curves, slot and spin axis position are optimized using Genetic Algorithms. The results indicate that, compared with the ellipse cutting method, the present method using more control parameters is more flexible to the earlier airfoil with more reasonable pressure distributions. Moreover, the endurance factor, take-off lift and lift-to-drag ratio of the designed slot airfoil are improved substantially. In addition, flaps with wide angle deflection play the role of deceleration during landing. The designed slot airfoil satisfies multiple demands and the present method is suitable for the MALE UAV design.