Abstract: A method for the analysis of steel frames considering the geometrical and material nonlinearities is presented. Large deformation of members including large rotation, large translation and large strain, the thrust effect on tha flexural stiffness are considered. Equilibrium and compatibility equations based on deformed configuration of structuresare derived for the analysis model, the geometric meaning of the nonlinear terms in the tangent stiffness matrix is discussed. A computer program for the whole range analysis of steel frames considering the geometrical and material nonlinearities is implemented, the load carrying capacity can also be determined.