Abstract: From the viewpoint of dynamics, dynamic stiffness method was proposed to study the vibration-resistant performance degradation properties of fiber-reinforced composite thin plate in thermal environment. Firstly, with the consideration of the effect of pulse excitation load, the dynamic stiffness values in thermal environment were solved by using the principle of energy method, plate and shell theory and modal shape superposition method. Meanwhile, the analysis process of vibration-resistant performance degradation of composite thin plate in high-temperature environment was summarized. In addition, a TC500 fiber/epoxy composite plate was taken as a study object, and through the comparison of dynamic stiffness, natural frequency, damping and modal shape results were obtained by the theoretical calculation and experimental test. The feasibility of the proposed method and the reliability of such a dynamic index have been verified, which can be used to quantitatively evaluate the dynamic performance degradation of composite thin plate in thermal environment.