Concrete is a non-homogeneous and anisotropic material. Modeling the mechanical behavior of Reinforced Concrete (RC) is still one of the most difficult challenges in the field of structural engineering. There are some factors which cause the mechanical factors of concrete in right dimension are not uniform and isotropic in high columns. In this research, critical load or stability of inhomogeneous reinforced concrete columns have been investigated and to complete this research, exact solving method, approximate solving method which include different methods of energy and exact finite element approach have been used.