A blood pressure gauge comprises a cuff, a gas pump, a pressure relief valve, a pressure sensor, a gas conduit, a MEMS microphone and a controller. The cuff has a gas bag. The gas pump is used for inflating and pressurizing the gas bag. The pressure relief valve is used for deflating and depressurizing the gas bag. The pressure sensor is used for detecting the pressure of the gas bag. The gas conduit connects the gas bag, the gas pump, the pressure relief valve and the pressure sensor to form a gas loop. The gas loop delivers gas among the gas bag, the gas pump, the pressure relief valve and the pressure sensor. The MEMS microphone is disposed at a specified location of the gas loop for detecting the Korotkoff sounds transmitted from the passing gas. The controller is used for monitoring and controlling the gas pump, the pressure relief valve, the pressure sensor and the MEMS microphone.
