The work aims to fabricate thermoplastic polyurethane elastomer composites with superior dielectric properties used for sensors. Octadecylamine was used to modify the oxidized graphene lamella. The oxidized graphene was partly reduced and modified through the technology of heat treatment. The modified graphene was dispersed into the matrix of thermoplastic polyurethane in the solution blending method and then formed by means of flocculation-hot pressing. Structures, dielectric properties and sensing properties of this material were tested. The octadecylamine was grafted to the oxidized graphene surface in the form of covalent bond. The X-ray diffraction showed that the octadecylamine modified through surface grafting increased the lamellar spacing. The dielectric elastomer filled with the modified graphene has higher dielectric constant and lower dielectric loss, and it exhibits good bending deformation-dielectric sensitive response.