The bifurcations of the flutter system of a 2D airfoil with cubic nonlinearity were investigated in this paper.Hopf bifurcation theory was applied to verify Hopf bifurcation at the critical point of flutter.The high-dimensional system was transformed into a lower-dimensional one by center manifold theorem.And

the complex normal form method of Hopf bifurcation was used to analyze the stability of the limit cycle

with the results consistent with numerical solutions.