Fabrication of C/SiC composites by using the heaterless chemical vapor infiltration (HCVI) technique, which is an improved technology based on the conventional chemical vapor infiltration, is reported for the first time in this paper. In the HCVI process, a gradient temperature field formed in the fiber preform overcomes the problems of slow diffusion and restricted permeability of gaseous reactant species to some extent, and the electro-deposition is necessary to accelerate the SiC deposition rates. The highest linear deposition rates of SiC matrix within inter-fiber pores are 0.33 mu m/h. Microstructures of the C/SiC composites are uniform, and the inter-fiber and inter-ply pores can be well infiltrated. The longitudinal and circumferential microcracks are found in the composites.