The　yellow　indium　oxide　nanoparticles　were　prepared　by　sintering　the　white　deposition　at　500　°C.　The　crystalline　indium　chloride　and　ammonia　were　used　as　the　starting　material.　The　results　show　that,　by　analyzing　the　particles　through　X-ray　diffraction　and　TEM,　the　particles　are　very　small,　spherical,　and　the　particle　size　is　about　40　nm.　The　direct-heat　components　made　from　indium　oxide　in　Cl2　and　NO2　was　tested　respectively,　the　component　is　far　more　sensitive　to　NO2　than　to　Cl2　at　low　heating　temperature,　and　the　status　is　reversed　at　high　heating　temperature.　©　2009　The　Nonferrous　Metals　Society　of　China.