A novel processable and high yield polyborosilazane (PBSZ) precursor for SiBNC ceramic fibers was synthesized via boron trichloride (BCl3), co-polymerization of trichlorosilane (SiHCl3) and methylamine (MeNH2), followed by trans-amination with NH3. The synthesized PBSZ precursor was characterized and the results showed that the polymeric precursor exhibited good melt–processability and green fibers with a diameter of 45µm could be easily obtained by melt spinning. The green fibers were subsequently pyrolyzed at 1200°C in nitrogen atmospheres to provide SiBNC ceramic fibers with a cylindrical hollow structure, ca.32µm in diameter and 720MPa in tensile strength. The green fibers had an approximately ceramic yield of 78% at 900°C.