In order to reduce product's weight, there are many thin plates structure in missile. Many nonlinear vibration phenomena are found in engineering region, but exact result is not available. In the paper, a high accuracy method on thin plate nonlinear vibration response was presented based on practice and actual engineering. After acquiring the mode damping ratio, the method is featured with high analytic accuracy resulting from the modified damping matrix. The calculation example indicates that the method and program are simple with enough analytic accuracy.