A new technology for preparation of TaC coating on Carbon/carbon composites is reported. TaC was turned from TaO2F·rH2O·TaF5, which was characterized by FITR, XRD and SEM. The morphologies of TaC coating at different temperatures were observed by SEM. At 1200 ℃, the TaC coating shows the particular form. When the heat treatment temperature increased to 1800 ℃, the TaC coating was mainly columnar. The formation mechanism of TaC is that Carbon atom diffuse into Ta2O5 deposit, which is coming from TaO2F·rH2O·TaF5 and reacted into TaC at high temperature. The morphology of TaC coating can be interpreted by the theory of Ta2O5 deposited nucleation