This study aims to design a novel control system for gasoline-engine driven hexacopter with variable-pitch, towards to increase the hexacopter's flight stability and endurance. The methodology is comprised of three steps: modeling of the hexacopter, control of variable-pitch propeller and gasoline-engine, and design of flight control system. First, the hexacopter's motion equation was derived with Euler-Lagrange method to comprehend the dynamics. Second, the appropriate control bandwidth of the variable-pitch propeller was turned out based on identification experiment, and a control method of a gasoline-engine utilizing a governor was proposed. Last, the control system was constructed utilizing Pixhawk flight controller and the PID gains were tuned. The control system has been verified by successful 22 minutes flight test. In conclusions, gasoline-engine driven hexacopters with variable-pitch could achieve long-endurance flight with stability and agility by designing the flight control system utilizing the presented methodology.