Micro-thermoelectric hydrogen sensor (μ-THS) is one of the promising candidates for hydrogen leak alarm system because of its simple structure, its unique and reliable working principle, catalytic combustion and thermoelectric (from heat to electric) conversion, and its sensing performance for wide-range of hydrogen concentrations. Catalyst is of great importance for the reliability in gas sensors. The integration of the catalyst is the key technology to make a sensor of high efficiency and high durability such as long-term stability. By controlling the catalyst preparation, the size, the thickness of the ceramic catalyst and the dispersion of Pt in the catalyst could be controlled. These are closely related not only to sensitivity but also to the long-term stability of the catalyst. We have monitored the performance of the μ-THS with ceramic catalyst over 3 months, to investigate the relation between the device preparation and the stability of the sensor.