The governing differential equations of motion for flexible aerofoil, which is coupled with plunge, pitch, and camber bending motions, were derived by using the Hamilton’s principle. The nonlinear aerodynamic forces of oscillating thin aerofoil were given with consideration of camber bending. The two-dimensional aeroelastic model of flexible aerofoil was presented and the flutter characteristics of flexible thin aerofoil were investigated. Numerical results show that the single camber bending motion is instability. When the characteristic frequencies of pitch and plunge modes are given, the flutter velocity is powerfully affected by the characteristic frequency of camber bending mode. When the characteristic frequency of camber bending mode is less than one of pitch mode, the flutter is dominated by the camber bending mode and the flutter velocity is much lower than one given by the classical pitch-plunge coupled model. When the ratio of characteristic frequencies of camber bending and plunge modes is 2.5, the flutter is dominated by the camber bending and plunge modes. When the ratio is greater than 2.5, it is dominated by the plunge mode. When the ratio is greater than 6.0, the pitch-plunge-camber bending coupled aeroelastic model is agreed with the pitch-plunge model.