To improve the strength of composite wing skin of a Unmanned Aerial Vehicle(UAV), the stacking sequence of honeycomb sandwich structure wing skin was designed optimally by a genetic algorithm. According to the design variables' discrete characteristics of the composite, the genetic algorithm based on an integral code strategy was presented. In consideration of the Tsai-Wu criterion, the fitness function was proposed and the constrain conditions were given by the stacking sequence principle of composite laminate layout. Then, the optimized stacking sequence scheme for skin composite structure was obtained by optimization design. Finally, the rationality of the composite laminate layout was verified by finite element analysis and static experiments. The experimental results show that the maximum deformations of the left and right wing tips are 116.02 mm and 105.36 mm,respectively, which meet the requirements that the best deformation is less than 180 mm. Ultrasonic inspection was performed and no damage is detected, which means that the wing structure meets the demands of engineering applications. An UAV with the composite wing skin was flown out successfully, and it verifies the feasibility of proposed design.