In this paper, the variational phase field model is adopted to analyze thermal buckling behavior of cracked functionally graded material (FGM) plates. Unlike existing works, the difference between neutral surface and mid-surface of FGM plates is taken into account in the present study. The kinematics of plate is based on first order shear deformation theory, while the crack is simulated by variational phase-field theory. The critical buckling temperature rises of cracked FGM plate is calculated, and the obtained results are then compared with those derived from extended isogeometric analysis by the authors and other numerical methods. We analyze the thermal buckling of cracked FGM plates for both cases: (a) the mid-surface coincides neutral surface, and (b) they are different between each other, and then showing their influence. We also investigate the effects of boundary condition and material properties on thermal buckling of cracked FGM plate. Through these results, it reveals the necessity to consider the difference between neutral surface and mid-surface in thermal buckling analysis.