Micrometer NbCx-C three-dimensional netted fibers were synthesized by the carbothermal method under 0.1 MPa of N2 ambient atmosphere at a relatively low temperature. Raw materials were commercial powders of Nb2O5 (99.95%), reactive carbon (99.99%), NaCl(99.95%) and sucrose (99.94%). The relationship of the fabrication processing with the composition, crystal structure and morphology of fibers was investigated. The formation mechanism was also proposed and discussed.