Prismatic steel beam-column of double symmetrical cross section with semi rigid end connections was analyzed using second order analysis theory. For this purpose, the stability functions are utilized to form the stiffness matrix in which the effect of axial force on the flexural stiffness as well as the effect of flexural deformations on axial stiffness are involved. Since, in forming the stiffness matrix, the interaction between the axial and flexural forces on the corresponding stiff nesses are taken into account, performance of slender members can be properly evaluated. The effect of semi rigid connections is included in the stiffness matrix by a power model. Finally, three examples are included in order to: (1) verify the validity of formulations, (2) compare the results obtained from the proposed second order analysis with those resulted from AISCILRFD method, and (3) investigate the effect of semi rigid connections on frame behaviour. The results are in an acceptable accordance with those obtained by others.