Abstract: ZrC coating, which may be a key layer to prevent the diffusion of fission products and bear the load in the next-generation TRISO coated particles, is an important research field of the advanced fuel element for high temperature gas-cooled reactor.The influence of chemical vapor deposition process on the phase composition of ZrC coating was studied with HSC-CHEMISTRY 4.1 code. It is found that the addition of enough hydrogen into carrier gas is necessary to obtain pure ZrC coating. Deposition at higher temperature increases with the concentration of ZrC and decreases with the concentration of free carbon in ZrC coatings. Moreover, the conversion rate of ZrC_l4 is increased also. But the influence is not obvious at higher temperature. the optimal deposition temperature is 1 400-1 600 ℃. The lowest concentration ratio of ZrCl₄ and CH₄ to obtain pure ZrC increases with the increase of the concentration of reactant. The reactant optimal concentration is 1.0%-2.0% for methane and more than 1.5 times of the concentration of methane for ZrCl₄.