Abstract: The dynamic stall of rotors limits the flight speed and maneuverability of helicopters. It has a complex mechanism and it is therefore difficult to get suppressed. Consequently, the dynamic stall is a major and persistent concern in the field of helicopter aerodynamics. This paper firstly introduces the development of experimental methods, semi-empirical models, and computational fluid dynamics (CFD) methods for the study of dynamic stall, and analyzes the advantages, disadvantages, and application scope of different methods. Secondly, research progresses on the dynamic stall mechanism of rotor airfoils and the influence mechanism of parameters such as aerodynamic shape of airfoil, angle of attack, and freestream conditions are sorted out. It is found that the dynamic stall under coupled freestream and pitch oscillations is more consistent with the flow characteristics of the rotor blade profile, and is one of the important directions for future research. Then, the development of design methods and concepts of rotor airfoils are described, and the advantages and disadvantages of the mainstream steady design and several unsteady design concepts are analyzed. Results show that the unsteady design can obtain an airfoil that can not only alleviate the dynamic stall but also improve the steady aerodynamic characteristics significantly. The unsteady design that comprehensively considers the motion and inflow of blade profile is a new direction for the current rotor airfoil design. Finally, the future development direction of rotor airfoil design is discussed, and a multi-level and multi-stage development concept of rotor airfoil design and blade design is proposed.