The invention relates to a gas sensing module and a wireless transmitting device and a wireless sensing system using the same. The gas sensing module comprises a piezoelectric resonator, a gas sensing unit and a modulation element. The piezoelectric resonator is connected to the gas sensing unit and an active circuit, so that the active circuit outputs a carrier wave related to the concentration of gas to be measured. The modulation element is connected to the piezoelectric resonator for setting the frequency or the amplitude of the carrier wave. The invention has less power consumption and low cost and is applicable to throwing occasions and multipoint detection.