Abstract: The abstract reaction of CH3SiH3with O has been studied by using variational transition-state theory, which is based on the information on geometries, frequencies and energies calculated by ab initio a-long the minimumenergy path. The mechanismof thisreaction hasbeen revealed. The rate constantsof the main path were calculated for the temperature range 2981000K. The result indicates that the variational ef-fect on thisreaction isgreat andthe tunnelingeffect isveryobviousat lowertemperature. The rate constants calculated match well with the experiment.