In this work, a new kind of composite nanofiber-based strain sensor with superior electromechanical properties was fabricated by using aligned thermal plastic polyurethane (TPU) nanofibers coated with multi-wall carbon nanotubes (CNTs). In order to improve the deposition efficiency and the fastness of CNTs coating on TPU nanofibers, bio-inspired dopamine (DA) was employed to modify the surface of the TPU nanofiber via a fast deposition method. (The composite nanofibers obtained were denoted as DATPU.) The electromechanical tests showed that DATPU/CNTs nanofiber membrane had a wide linear working range of 370% in the direction parallel to the nanofibers (P-DATPU/CNTs), a high gauge factor of 22.0 and a high linear coefficient of determination (r(2)) of 0.997. P-DATPU/CNTs nanofibers also exhibited excellent durability during stretching-releasing test for 5000 cycles. The P-DATPU/CNTs composite nanofibers demonstrated high sensing performance in detecting human motions of finger and elbow bendings.