The reaction of methanol with silicon was carried out in a mixed bed reactor into tetramethoxysilane at 210 ℃. In order to determine the kinetics of the reaction per reaction site on the silicon surface, a flowrate transition technique was employed. A kinetic study showed this reaction was in linear relationship with contact mass and independent on the concentration of methanol. This result indicates that the rate-determining step is not the chemical process involving methanol but the diffusion of silicon to form silylene intermediate.