Abstract: The composite material has typical nonlinear characteristics. Its nonlinear stiffness is very important for the system design and analysis. The random vibration is ubiquitous in the environment, and the identification of nonlinear parameters in the practical environment gives more reasonable results. A method of identification of nonlinear parameters based on the random decrement method and the continuous wavelet transform is presented. And a program of identifying the nonlinear stiffness based on the random vibration response is developed. A numerical example of a single freedom nonlinear system with cube stiffness is given to validate the method and the program. The nonlinear characteristics of the typical composite material structure are studied. It is shown that the method of identification of nonlinear parameters enjoys a high precision, and different resonant order of a multi freedom system has different nonlinear characteristics. The present method is useful for the nonlinear parameter identifying and modeling in a random vibration environment.