Abstract: Using trichloromethylsilane (MTS) and H₂ as precursors, the deposition kinetics of silicon carbide (SiC) was studied by chemical vapor deposition (CVD) process at 900-1 050℃, H₂/MTS mole ratio of 4-20 and residence time of 0.4-1 s. The results show that the variation of SiC deposition rate with process parameters in different reactors is obviously different. The average deposition rate of SiC in the reactor with length diameter ratio of 7∶6 increases with the increase of temperature, while the average deposition rate of SiC in the reactor with length diameter ratio of 7∶2 first increases and then decreases with the increase of temperature. Moreover, the deposition of SiC along the reactor with length diameter ratio of 7∶6 has the characteristics of multiple steady states. The variation of SiC deposition rate at different H₂/MTS mole ratios is basically consistent in the two reactors. Although multiple preferential deposition positions along the SiC path appear in the reactor with length diameter ratio of 7∶6, the inhibition effect of H₂ on SiC deposition is greater than that caused by reactor size effect. The results show that the average deposition rate of SiC in the reactor with length diameter ratio of 7∶6 decreases with the increase of residence time, but the deposition rate along the path does not decrease monotonically due to the effect of reactor size; both the average deposition rate and the deposition rate along the path of the reactor with length diameter ratio of 7∶2 decrease with the increase of residence time and then tend to be stable. The flow field and temperature field of two kinds of length diameter ratio reactors were simulated by COMSOL software. It is found that the reactor with length diameter ratio of 7∶6 produces obvious radial velocity difference, and the axial and radial temperature difference are large, while the flow field and temperature field of deposition reactor with length diameter ratio of 7∶2 are more uniform. The actual process parameters and theory caused by the size effect of the reactor were analyzed. The deviation of process parameters is the reason for the difference of SiC deposition kinetics in different length diameter ratio reactors.