Abstract: In nature, flying creatures flap their wings to generate the lift which is necessary for flight. Most birds change the flight patterns by using the wing muscles to move wings with different states of the tail. Without tails, insects are capable of maneuverable flight through their chest and abdomen muscles and other structures such as hind wings. Due to high mobility and high energy efficiency, researchers develop a variety of flapping-wing aerial vehicles based on the bionic principle in order to improve their flight performance. However, the flapping-wing aerial vehicle is unsteady and time-varying. Low Reynolds number and unsteady eddy are the important characteristics of the flapping-wing aerial vehicle, which are different from the traditional aircraft. The Reynolds number of the traditional aircraft is larger, so the air viscosity is small enough to be ignored. However, the air viscosity of the bionic flapping-wing aerial vehicle is large at low Reynolds. If researchers adopt the conventional aerodynamic configuration, it will cause the problem of insufficient lift. In addition, the traditional aerodynamics theory cannot explain the high lift of the flapping-wing aerial vehicle, and the mature technologies in traditional aircraft design cannot be directly applied due to the low Reynolds number. Because of the periodic movement of the flapping wing, it is difficult for researchers to analyze the aerodynamic model accurately. The autonomous flight of the flapping-wing aerial vehicle is confronted with great challenges. To solve this problem, researchers study the flight principle of birds and insects. Then, the attitude control, the position control and the stability analysis of flapping-wing aerial vehicles are studied. Based on robust control, neural network and other methods, a number of control strategies are proposed to realize autonomous flight of flapping-wing aerial vehicles. Researchers adopt control methods such as adaptive controller combined with linearization method to control attitude. Position control is achieved by setting up hierarchical controller and other approaches. In addition, perturbation observation is used to deal with the uncertainty of the system to improve the stability. In this paper, the investigation on the flight control strategy of different-scale flapping-wing aerial vehicles is summarized. It can be seen that the current research on the flight control of the flapping-wing aerial vehicle is mostly in the prototype phase. Most of the theories have not been verified in actual flight. Therefore, the flight control theory needs to be combined with the actual mission to promote the application of the flapping-wing aerial vehicle. Finally, the future trend of the flapping-wing aerial vehicle is pointed out.