Abstract: The thermal-mechanical coupling buckling behavior of simply supported porous functionally graded beams was studied by classical Euler beam theory and high-order sinusoidal shear deformation theory. The correlation between material properties and temperature was considered, and the material properties of the porous functional graded beams were described by modified Voight mixture rule with porosity. The iterative algorithm was used to solve the critical thermal-mechanical coupling buckling temperature of the porous functionally graded beams under uniform, linear and nonlinear temperature rise (considering the heat conduction effect). And the influence of the parameters such as gradient distribution index, porosity and slenderness ratio on the critical buckling temperature were discussed. By comparing the results of ABAQUS and the literature, the theory is proved to be reliable, and the high-order sinusoidal shear deformation theory can obtain more accurate results than the classical Euler beam theory. The results show that in the analysis of the thermal buckling of functionally graded materials, the temperature dependence of material properties must be taken into account. Otherwise, the critical buckling temperature may be over-estimated by 10%-30%. As the porosity of the material increases, the equivalent elastic modulus of the functionally graded material will decrease, namely the structural stiffness will be weakened, while the critical buckling temperature of the structure will increase greatly.