This article presents the results of theoretical research of the piezoresistive properties of doped single-walled carbon nanotubes (SWNT ) of two structural modifications : «arm-chair» and «zig-zag» types. The electronic structure of nanotubes doped by the substitution point defects is calculated within the Hubbard and Anderson models taking into account the Coulomb electron correlation in the «Hubbard-I» approximation. Nitrogen and boron were chosen as the acceptor and donor impurities, respectively. The elastic conductivity tensor — main characteristics of the piezoresistive effect was analytically calculated, their dependence on the concentration of defects and the magnitude of the strain of tension and compression was analyzed.