The invention provides a water-gas separating and treating device which comprises a closed cylindrical container. A drainage pipe used for inputting water-gas mixtures into the container and a gas outlet pipe used for discharging gas separated from the water-gas mixtures are arranged on the upper surface of the container. The inflowing end of the drainage pipe is connected with the positive pressure side of an extraction pump station, and the outflowing end of the drainage pipe is arranged at the position, close to the lower surface of the container, in the container. The gas inlet end of the gas outlet pipe is arranged on the upper surface of the container, and the gas outlet end of the gas outlet pipe is connected with the negative pressure side of the extraction pump station. A water outlet is further formed in the side wall of the container. According to the water-gas separating and treating device, water is used for submerging the low input end of the water-gas separating and treating device to achieve the water sealing effect. On one hand, water and gas are guided in through the function of negative pressure drainage, and the water and the gas are separated through the water sealing effect. On the other hand, the gas is drawn into an extraction system through the negative pressure drainage, and water-gas separation is effectively achieved.