A novel kind of supramolecular polymer filament with a diameter of 2-5 mu m was artificially synthesized, which is in fact a bundle of self-assembled nanotubes with a diameter of about 40 nm. The filament can be drawn from a special alkaline aqueous solution directly and free standing in room temperature, which has never been performed earlier. A microtensile tester was developed with the aid of an electronic balance to investigate the mechanical properties of the new filament. Monotonic and load-unload tensile tests were performed, respectively. The maximum tensile strength and the elastic modulus of the filament were 23.8 MPa and 1.9 GPa, respectively, which were higher than previous supramolecular polymers and comparable to some covalent-linked polymers.