A highly flexible and stretchable strain sensor has been prepared by coating chemical reduction of graphene oxide on electrospun polyurethane nanofiber mats. The sensor exhibits an ohmic behavior regardless of applied strains and the current monotonically increases with the increase of the tensile strain. The morphology and stability of electrospun polyurethane nanocomposite mats were also studied. The flexible and stretchable strain sensor has great potential for practical application such as efficient human-motion detection. This cheap and simple process of graphene layer provides an effective fabrication for graphene stretchable electronic devices and strain sensors due to excellent stability and electrical proper.