This paper studied the nonlinearity properties of a simply supported rectangular graphiteexpoxy laminated plate, excited by twoterm harmonic forces. The nondimensional Duffing nonlinear forced vibration equation was deduced by using Galerkin method from the vibration differential equation.The amplitude frequency response equation of the system steady motion under combination resonance was obtained by the method of multiple scales. Based on Lyapunov stable theory , the critical conditions of steadystate solutions stability were obtained .By examples, the influence of different parameters on nonlinear combination resonances properties of system was analyzed. Finally the conclusion of graphiteexpoxy laminated plate’s nonlinearity properties excited by twoterm forces were presented.