Abstract: We use pressurized thermogravimetry to carry out thermogravimetric analysis of high pressure sealing material used in oxygen respirator with positive pressure. Through establishing the thermogravimetric analysis curve of nylon, teflon, nitrile rubber, fluorine rubber, we get ignition point under different oxygen pressure and determine that ignition point of material gradually reduces with the increase of pressure, analyze that the heat-release of high pressure sealing material oxidation reaction is constantly accelerated and the accumulated heat will lead to fire of sealing material. Selecting high oxygen index material is conductive to reduce the fire possibility of high-pressure gas supply system of oxygen respirator.