The nonlinear vibration of the telescopic cantilever composite plate subjected to the in-plane excitation and the third-order aerodynamic force is studied when it is in the deployment and retraction. Based on classical laminated plate theory and Hamilton principle, the nonlinear partial differential equation of the telescopic cantilever plate in the process of deployment and retraction is established. Then, the Galerkin method is used to discrete the nonlinear the partial differential equations into the ordinary differential equations with time-varying coefficients. Frequency variation diagrams,time history diagrams and phase diagrams are obtained by numerical methods. The influence of axial velocity, width-to-thickness ratio and slenderness ratio on the nonlinear dynamic characteristics of the telescopic cantilever composite plate is discussed. The results show that the larger the axial moving speed is, the more likely it is to cause the amplitude to diverge when the telescopic cantilever plate is deploying at a uniform speed. However, amplitude divergence does not occur in the retracting process.