The invention discloses an automatic vacuum drainage device which structurally comprises a pressure gage, an air outlet pipe, a flange, an air inlet, a cylinder, stand bars, supporting cushions and drainage pipes, wherein the top center of the cylinder is fixedly connected with the bottom of the air outlet pipe; the pressure gage connected with the obverse side of the air outlet pipe is mounted onthe obverse side of the air outlet pipe; the pressure gage is positioned above the flange and is connected with the cylinder; the air inlet is formed in the top of one side face of the cylinder; andthe air inlet and the cylinder are of an integrated structure. The automatic vacuum drainage device has the function of automatic drainage, can automatically drain water when water is accumulated to certain amount, does not need two sets of collecting tanks for liquid drainage through replaced application, saves manpower, reduces man-hour, and is high in production efficiency and simple and easy to operate.