The subcritical problem of wing flutter system with freeplay nonlinearity was addressed by introducing the NES(nonlinear energy sink) technology to improve the critical velocity of the system′s limit cycle oscillation. A dynamic model of flutter system with NES control for wings with freeplay nonlinearity was established, and the suppression effects of NES parameters such as mass ratio, frequency ratio, damping ratio, and relative position on the limit cycle oscillation of the flutter system were analyzed. The influence of NES parameters on the critical speed of the limit cycle oscillation of the flutter system was also investigated. The results show that a larger damping ratio can stabilize the system at a smaller natural frequency ratio but required a more stringent location requirement for the NES, i.e., closer to the leading edge of the wing. On the other hand, a smaller damping ratio results in a smaller NES mass required to stabilize the limit cycle response of the flutter system. When the NES location is closer to the leading edge of the wing, increasing the natural frequency ratio significantly improve the suppression effect of limit cycle oscillation, and increasing the mass ratio also significantly improve the suppression effect and critical speed of limit cycle oscillation. Additionally, a smaller damping ratio of the NES results in better suppression of limit cycle oscillation in the flutter system.