In this paper, the Timoshenko porous beam model with a coordinate system placed on a neutral plane is used in the buckling analysis. Three types of porosity distributions, namely uniform, symmetric, and asymmetric through the height directions are considered. Equation system of equilibrium and boundary conditions for beams are set based on the principle of minimum potential. Analytical solution based on direct solution method was established for different types of boundary conditions of beams. The accuracy of the present solutions is verified by comparing the obtained results with those of existing literature, in which the reference coordinate axes are located on mid-surface. The influence of material parameters, geometry and boundary conditions on the critical load of a beam were analyzed through numerical examples.