Abstract: TG DSC MS(Thermogravimetry Differential Scanning Calorimetry Mass Spectrometry)coupling techniques were used to make a simultaneous characterizing study of the behavior for the carbon nanotube(CNT) reinforced SiO 2 composites during the process of thermal decomposition. Nine kinds of expected positive ions such as C + ( m/z 12), OH + ( m/z 17), H 2O + ( m/z 18), CO 2 + ( m/z 28), etc, were measured by multiple ion detection(MID). CNT/ SiO 2 composites were fabricated by hot pressure sintering the mixture powders by rapid sol gel method. The complete combustion of free carbon was presented at the temperature of about 500~730℃. Meanwhile, the preliminary exploration for the thermal decomposition mechanism of CNT/SiO 2 composites has also been done in this work. CNT/SiO 2 composites have been sintered under the temperature of 500℃ for 1h. It would be useful for the preparation of the CNT/SiO 2 composites.