Abstract: The nonlinear dynamic characteristics of aluminum honeycomb sandwich board, as a widely used compound material in spacecraft, are studied in this paper. With random vibration tests in different test levels, nonlinear frequency response functions (FRF) are obtained; and it is shown that as the excitation level increases, the FRF decreases in magnitude, and the damping ratio increases, which is consistent with the model with nonlinear damping, with FPK transform and equivalent principle method being combined. That reveals the nonlinear damping characteristics in aluminum honeycomb sandwich board. This study provides a theoretical guidance in choosing a model for a nonlinear dynamic system.