Abstract: The large-amplitude vibration of a fully clamped or simply supported thin isotropic rectangular plate subjected to a concentrated harmonic force is calculated numerically to obtain the surface velocity distribution,and the radiated sound power of the plate is calculated based on the acoustic radiation modes.First,the nonlinear finite element equation of plate vibration is derived by using the finite element theory according to von Karman geometric nonlinear strain-displacement relations.Then,the equation is transformed into modal coordinates by modal reduction method and to be solved by Newmark's method,thus the surface velocity distribution of the plate is obtained.Finally,the total radiated sound power under single-frequency excitation is calculated based on the acoustic radiation modes.The use of finite element modal reduction method provides great convenience for the direct numerical integration of nonlinear finite element equation of motion:(1) equation decoupling;(2) reduce the system DOF.The number of modes used in the modal superposition is also discussed,and it is shown that using the first few modes is enough to predict the vibration response of the plate.Finally,the frequency drift under geometric nonlinear effects is confirmed by the calculation.