Abstract: This article examines the technique of describing the stress-strain state (hereinafter - the SSS) of the normal section at the top of the inclined crack, based on nonlinear deformation model. Normal section's analysis will assess the uniaxial SSS of any concrete element subjected to bending, compression with bending, stretching or stretching with the bend. Parameters of SSS of the normal section are the normal and shear stresses, the relative deformation of compression and tension. Data acquisition of this parameters using the nonlinear deformation calculation, created the prerequisites for describing SSS oblique section. Algorithm is built using modern mathematical apparatus in the computer environment «MathCAD». Used abilities of mathematical analysis allowed foprming a realistic settlement of the normal section diagram at the top of the inclined crack. By implementing real chart of material deformation, the algorithm is allowed to build a more accurate diagrams of normal and shear stresses in the normal section on the basis of steps, iterative and integrated processes. During algorithmization work, section were identified important components of its work: the value of the centers of gravity of plane diagrams of stress and strain, the exact coordinates of the boundaries of the compressed, stretched and destroyed sectional areas. The study was applied and refined new ways to describe the theory of concrete strength.