The utility model provides an automatic ware that drains of gas drainage, is applicable to the ponding of getting rid of in the gas drainage pipeline. Become by gas extraction pipe, connecting pipe and the U type nest of tubes. At connecting pipe of the lower of gas extraction pipe installation, by flange joint between connecting pipe and the gas extraction pipe, the lower extreme of connecting pipe is equipped with the valve and connects a U type pipe, an airtight stopper is installed to U type pipe end, airtight stopper apart from gas extraction pipe's height for (img file='DDA0001222153310000011. TIF'wi='163'he='95' /) wherein P adopt the biggest negative pressure in the pipeline for taking out, rho is density of water. Installation gas drainage is automatic when turning on the water the ware, and tight airtight stopper is closed, is filled in to the valve, places the U type mouth of pipe in water tank after the installation, pulls out airtight stopper and opens the valve, treats toremove the water tank after the water column no longer rises in the U type pipe. This invention easy operation, stable performance, security are strong, have extensive practicality.