Abstract: Tubes, as important engineering structures, are widely used in various fields, its geometric characteristics are special, and the traditional beam theory can not satisfy the boundary condition that the shear stress on its inner and outer surfaces is zero. It is crucial to adopt a suitable beam theory to study it. A modified high-order shear deformation beam theory was used to study the nonlinear bending behavior of porous functionally graded material tubes under the hygro-thermal environment. Considering temperature-dependent material properties, basing on the modified high-order shear deformation beam theory and von Kármán nonlinear theory, the nonlinear bending control equations of porous functionally graded material tubes were derived by the principle of minimum potential energy. The control equations were solved by the two-step perturbation technique. The effects of porosity distribution types, porosity, gradient index, inner radius, humidity and temperature on the nonlinear bending behavior of the tubes were discussed by numerical examples. The nonlinear bending behavior analysis method of porous functionally graded tubes under hygro-thermal environment was proposed, and the semi-analytical solution of this problem was obtained, which will provide a theoretical basis for optimizing the structure and material parameters of porous functionally graded material tubes. The results show that when the porosity is relatively high, the porous functionally graded material tubes with uneven pore distribution models exhibit superior resistance to bending deformation compared to those with even pore distribution models. Consequently, in practical lightweight design processes, uneven pore distribution models are preferably adopted.