The effect of low-layer graphene nanoparticles (LLGNP) at concentration from 0.002 to 0.1 wt.% on physical-mechanical and structural parameters of multi-block polyurethanes based on oligodiethyleneglycol adipinate, 2,4-toluylene diisocyanate and 1,6-hexamethylene diisocyanate mixture and bifunctional chain elongation agents, 2-aminoethanol and 1,4-butanediol has been studied. Three methods for LLGNP addition in polymer were compared: (1) in a reaction mixture at the polymer synthesis on a macrodiisocyantate formation step (in situ 1 method); (2) in the polymer solution at a final reaction step (in situ 2 method); and (3) in polymer melt (ex situ). It has been shown that using of the in situ 2 method provides an increase in Young's modulus of the nanocomposites. For ex situ method, a significant increase in tensile strength of the material with growth of LLGNP concentration was detected.