The article consider a methodology for calculation the sucker rod string of progressing cavity pump. Method of calculation involves determining the axial, torsion and bending loads acting on the rod string during their rotation, as well as their rise during tripping operations. Method of calculation is given only for three-interval wells including vertical and inclined sections of the wellbore, as well as the section of the wellbore with the local curvature. The article describes the method of calculation of the stress in the metal sucker rod with the experimentally obtained dependence of the joint impact of the oil viscosity, the relative velocity of the rubbing bodies and specific normal load, as a result, of research of friction pairs of elements sucker rod for progressing cavity pump. The article consider the friction coefficients depending on the number of Sommerfeld for pairs of friction (coupling on tube, rods on tube, rod on centralizers and the pump rotor on the stator). The proposed method allows designing rod string with the boundary and hydrodynamic friction, and predicting their optimal parameters at the design stage. An integrated approach to the calculation will allow developing appropriate technical solutions for further improving the design elements of the rod string, in order to reduce loads and power consumption of the installation.