Abstract: Due to the heterogeneous property of plates or shells made of functionally graded materials(FGM), the stretching-bending coupling effect in their constitutive equations exists and applying in-plane compressive edge loads to such plates will cause the pre-buckling coupling deformation to appear under some conditions, that is, transverse deflection is initiated, regardless of the magnitude of the loading. Based on the classical nonlinear plate theory, basic equations for stability of a functionally graded circular plate under uniform radial compression or thermal load are derived and the pre-buckling coupling deformation is taken into account in analysis, and then a method is given to identify whether or not true bifurcation buckling can occur. A shooting method is employed to numerically solve the resulting equations and the effects of the pre-buckling coupling deformation on the stability of FGM circular plates are studied under various boundary conditions and applied loading conditions.