A new curing method, chemical vapour curing (CVC) for polycarbosilane (PCS) fibers using unsaturated hydrocarbon (cyclohexene) vapour was studied. The low oxygen content SiC fibers were prepared and when the oxygen content in fibers was lower than 4.0%, the maximum tensile strength reached to 3.8GPa. The relationship between the tensile strength and the oxygen content of the fibers was investigated. The structure and composition of SiC fibers were also characterized by element analysis, FT-IR, XRD and XPS. Compared with that by air curing method, SiC fibers with less oxygen and better mechanical properties were prepared by CVC method.