The problem of a concrete cross section under flexural and axial loading is indeterminaterndue to the existence of more unknowns than equations. Therefore proper analysis ofrnreinforced concrete member is important for understanding the actual behavior andrneconomical use of sections. The main objective of this Thesis is to investigate geometricrnnonlinear effect of axial load on flexural deformation of reinforced concrete members.rnFlexural members, which are subjected to gravity central point load, externalrncompressive axial load and combination of those load with different support conditions,rncross section and span length are analysed using linear and geometric nonlinear methodrnof analysis to investigate the effect of axial load on flexural deformation of flexuralrnmembers. The percentage variation of flexural deformation under linear and geometricrnnonlinear analysis for various conditions of members is calculated to achieve thernobjective. Finally four story reinforced concrete residential building frame is analysedrnusing linear and geometric nonlinear analysis. Both linear and geometric nonlinearrnanalysis is done by using STAAD Pro and linear analysis using FEM based code usingrnScilab and ETABS. After the analysis of flexural members it is found that: Thernpercentage variation of linear and geometrical nonlinear deflection is very high for beamrnwith lesser depth. It was found that the support conditions also affect variation ofrndeflection for the linear and nonlinear cases. The variation between linear andrngeometrical nonlinear deflection of beam is negligible when the ends are fixed. But forrnthe same beam with simply supported end conditions the defections were found havingrnvariation up to 17.571 percentages. Geometrical nonlinearity is more when the load isrnvery high and lesser depth. At the initial stages of loading behavior of beam is linear onlyrnand it behaves nonlinear when we go for higher loads. As the deforming of middle planern(Neutral axis) starts, the stiffness of structure increases (axial stiffness is added withrnbending stiffness).Thus the beam becomes stiffer progressively. It is a positive aspect ofrngeometric nonlinearity.