In this work, preparation of TaC-SiC fibers derived from Ta-doped polycarbosilicon precursor are reported. Ta-doped precursor was prepared by using nanometer tantalum powders (nano-Ta) and polycarbonsilane (PCS), according to the quality of tantalum powders and PCS at 10wt%, via ultrasonic and ball mill mixing method. TaC-SiC fibers were prepared after melt-spinning, electron beam irradiation and heat-treatment. The composition, structure and pyrolysis process of the obtained green fibers were investigated by IR, TG, XRD, SEM and so on. The results show the evolution of volatile gases is inhibited via introduction of nano-Ta in the precursor and the yield of precursor was increased to 69.32 wt%. TaC ceramics could be prepared via reaction of tantalum powders with free carbon in the fibers. The ceramic fibers were compact and smooth. Thus, TaC-SiC fibers could be prepared using the doped method.