In the work, the microscopic mechanisms of uniaxial deformation and fracture of graphene are investigated in the framework of quantum mechanics. The spatial structure of graphene sheet, the heat of its formation and the deformation forces are calculated at the nanoscale level. The deformation and fracture are described by mechanochemical strain coordinates and the deformation forces are calculated as energy gradients of the mechanochemical strain coordinates. Using these forces and a conventional macroscopic approach with relations of the linear theory of elasticity, the strain and fracture characteristics of graphene were determined. Despite the clearly defined nanoscopic character of the deformation forces used in calculation of the strain characteristics, the calculation results agree well with available experimental data. © 2009.