Research in Hydrogen Gas Sensor that feature a low cost combined with very high sensitivity, low thermal drift and low power consumption is required for application fields such as the hydrogen fuel cell vehicle, the fuel cell power plant. We have investigated silicon micro-machined hydrogen gas sensors for fuel cell vehicle with low power consumption and very high sensitivity shown in Figure1. Since the devices has only multi layer membrane(SiO2/Si3N4/SiO2)[Figure2] using clean etching technology and specially manufactured Pt/Al2O3 catalyst[Figure 1], device characteristics are stabilized for sudden change of atmospheric temperature. In the characteristics, low thermal drift is most important parameter when the devices actually used severe environments where atmospheric temperature is varied suddenly like thermal-shock. The thermal drift characteristic is stabilized for high temperature that 500ºC at 4.5V shown in Figure3. It is considered that the thermal drift must be researched more severe environments(-40ºC to 300ºC) to apply actual application fields. As shown in Figure4 and Figure5, the response time within 2sec is obtained with power consumption within 100mW. The measured results is obtained using hydrogen gas sensors measurement system for verification. In the results, the output voltage is 80mV at 2% hydrogen shown in Figure5. It is considered that power consumption, response time and output voltage will be decreased with catalyst and micro-heater optimization. The measured hydrogen reaction temperature of catalyst using infrared thermal measurement systems is increased about 60ºC at 2% hydrogen shown in Figure6. In the extended abstract, the detailed characteristics will be presented.