Abstract: Facing constantly varying airflow conditions, birds in nature adjust their flapping amplitude of wings to enhance flight efficiency. This behavior, termed variable-amplitude flight, is mimicked by the proposed flying robots, and a variable-amplitude flight strategy based on motor closed-loop control is proposed. Firstly, a closed-loop model of wing flapping angle is built, considering the dynamic model of the motor and the dynamic characteristics of wing motion. Then, a controller is designed to achieve precise control of wing flapping angle. Building upon this, a variable-amplitude flight strategy with gliding functionality is devised and its effectiveness is validated through numerical simulations. A solution is provided for the practical application of the variable-amplitude flight strategy for various medium to large flapping-wing flying robots. This solution is based on a falcon-inspired flapping-wing aircraft platform, which is equipped with sensors to collect wing flapping angles and a Falcon 2.0 flight control board to run the variable-amplitude flight control algorithm. The total mass of the equipped platform is increased by less than 30 g. As the results of the ground experiments, the wings reach the specified glide angle within 0.2 s, and variable-amplitude flight can be achieved with wings flapping at variable frequencies between 1~4 Hz. Additionally, ground turntable experiments demonstrate the proposed strategy can further improve the airflow utilization efficiency, with a 14.7% increase in the lift compared to traditional cyclic flapping methods. Flight tests show that the aircraft can achieve stable gliding within 0.5 s and can also perform variable-amplitude flight at frequencies of 2~3 Hz, fully validating the effectiveness of the proposed variable-amplitude flight strategy. The proposed variable-amplitude flight strategy enhances the degrees of freedom of the wing flapping motion of flapping-wing aircraft, providing an effective solution for performance optimization and practical applications of flapping-wing aircraft.