The utility model relates to an evacuation auxiliary device. Its characteristics are: including pressure vessel (5) of top end opening, the opening part welding on this pressure vessel (5) top has ring flange (1), and this ring flange (1) is equipped with three through -hole through fastener and apron (3) fixed connection on this apron (3), and the welding has one connecting pipe (2) on every through -hole, and all installs a vacuum valve in the mouth of pipe department of every connecting pipe (2), wherein also be equipped with three through -hole on pressure vessel (5) lateral wall, the welding has a steel pipe on every through -hole, and these three steel pipes are first steel pipe (6), second steel pipe (7) and third steel pipe (4) in proper order. The utility model provides an evacuation auxiliary device uses this device to increase substantially evacuation efficiency when the residual voltage is monitored to the accuracy in the work progress through identification on probation.