The thermal conductivity, emissivity, specific heat capacity and thermal diffusivity of SiNx thin films which are widely used in semiconductor and microelectronics MEMS are measured using a novel experimental method which combines the heater and the bolometer in one unit. The obtained reliable thermal properties are very useful for microelectronic circuits design and mask processing. The experimental data show that the thermal conductivity, emissivity and thermal diffusivity of SiNx thin films are much lower than those of the bulk and depend on the temperature and thickness of the thin films, and the size effect of SiNx thin films is notable. However, the specific heat capacity of SiNx thin films is almost the same as that of the bulk.