Subcritical flutter caused by aerodynamic or structural nonlinear factors causes limit cycle oscillation in aircraft below the linear flutter critical velocity. This phenomenon leads to deteriorations in the vibration environment of airborne equipment, degradation of flight control performance and other problems, posing a hidden danger to safe flight within the flight envelope. In this paper, a subcritical flutter time-delay feedback controller based on pitching velocity signal is designed for a 2-DOF wing section with nonlinear stiffness in pitch degree of freedom. At first, a nonlinear aeroelastic mathematical model of a 2-DOF wing section is established by using Lagrange principle. Then, the method of multiple scales is used to derive the analytical solution of the closed-loop control system with time-delay pitching velocity feedback. Subsequently, the stability boundary of the flutter system is determined through stability switching theory, providing the parameter range for the subcritical flutter delay controller. Finally, the effectiveness of this subcritical flutter time-delay feedback controller is verified through closed-loop numerical simulations of nonlinear aeroelastic systems under various wind speeds. The simulation results demonstrate that an aeroelastic time-delay feedback controller based on pitching velocity signal can convert subcritical flutter into beneficial supercritical flutter and significantly reducing limit cycle amplitudes.