Dynamic behavior analysis of the nonlinear aeroelastic system is one of the interesting topics among researchers that have been studied in recent years. Nonlinear airfoil instability and behavior analysis in subsonic flow are one of the main parts in this field. Aeroelastic systems are characterized by complex nonlinear phenomena due to structural oscillations coupled with the fluid dynamic. The coexistence of phenomena, such as limit cycle oscillation and chaotic vibrations induced by the fluid, can lead the dynamic systems to instability such as flutter which can decrease the system performance, as well as the damage of the structure itself.Historically, the main approach to analyze the dynamic instability of nonlinear aeroelastic systems has been developed by Theodorsen [1] in the frequency domain. His theory aimed to model the aerodynamic loads on an airfoil when the wake releasing is considered as a memory effect on the global fluid-structure interaction dynamic. Wagner proposed a time-domain analysis where the memory effects are represented by convolution Volterra integrals [2]. Both these traditional models are linear, but, in many cases, the dynamic equations of an airfoil became nonlinear due to the presence of nonlinear elements (dampers, stiffness) or for the instabilities generated from the fluid-structure interaction. The nonlinear aerodynamic model in the time domain can be solved by numerical techniques or analytical methods. In the first case, the solutions such as the finite difference method, Runge-Kutta,