A micro gas sensor is disclosed including a substrate; an open cavity formed in the substrate; an electrode pad separation groove formed on the substrate; a first and a second electrode pads formed over the substrate and electrically insulated from each other by the electrode pad separation groove; a micro heater connected to the first electrode pad and configured of a bridge structure suspended over the open cavity; a first sensing electrode extending from the first electrode pad and suspended over the open cavity; a second sensing electrode extending from the first electrode pad and suspended over the open cavity; and a gas sensing film electrically coupled to the micro heater and filling a gap between the first and the second sensing electrodes.