Abstract: Thermal performance of MEMS based micro-hotplate was investigated by a simplified model both in vacuum and in atmosphere. The influence of a homogeneous block inside the heater was also studied. The results demonstrate that for a ring-shaped heater with a homogeneous block in vacuum, a good uniformity of the temperature can be obtained and in atmosphere the ring heater should be narrow and extend to the inner part for better uniformity. The results obtained by coupled thermal-electrical simulation using the finite element method（ANSYS） software results are in good agreement with the measured results. Furthermore, an optimized heater giving a uniform temperature all over the active area is suggested.