Abstract: Lyocell fibers filled with various amounts of carbon black were prepared and used as the precursors of carbon fibers to increase the yield and the mechanical properties of Lyocell-based carbon fibers. The structure and properties of these samples were investigated by WAXD, TGA, SEM and tensile strength. The WAXD results showed that carbon black filled Lyocell fibers still had a cellulose II crystal structure and retained the characteristic peak of carbon black at the same time. Moreover, the heat stabilities of these fibers had no obvious change from TGA curves. The carbon yields of Lyocell fibers filled with 10% and 30% carbon black at 1000℃ were increased by 4.4% and 17.1%, respectively. The SEM results showed that the surface and the cross-section of carbon black filled Lyocell fiber was smooth and round, consistent with the requirements of a carbon fiber precursor. WAXD patterns of the carbon fibers showed that the structure of carbon black filled Lyocell-based carbon fibers was different from that of general Lyocell-based carbon fibers. The tenacity and modulus of 10% carbon black filled Lyocell-based carbon fiber were increased by 22% and 42%, respectively. At present, a carbon fiber with a tenacity of 0.8GPa and modulus of 70GPa has been obtained on a large-scale.