Abstract: Numerical methods and the harmonic balance method are adopted to study the influence of coulomb friction on aeroelastic airfoil systems. The initial condition sensitivity in aeroelastic systems with coulomb friction is analyzed, and the differences between damping and coulomb friction in conventional dynamic equations are illustrated through the energy expression. The result shows that coulomb friction can improve flutter speed which is related to the initial condition. Apparently, the increase of pitch damping or introduction of coulomb friction can improve system flutter speed and reduce pitch amplitude. However, for linear systems with damping, changes in initial conditions do not change the system energy balance, and the introduction of coulomb friction changes the system energy balance and makes the flutter speed and the flutter frequency related to the initial condition.