The utility model relates to a closed type speed reducer for starting vertical lift people's air defense door anti -flooding door mainly comprises with rising to rise the device perpendicularly the headstock gear, perpendicular rises the device and includes two sets of hook assembly and rope, the headstock gear includes that two sets of reel devices, one nonstandard rise reduction gear, one and play to rise brake motor, a synchronizing shaft, the two sets of reel devices include to turn left that the wound packages is put and is turned right the wound packages puts, synchronizing shaft connects a gear coupling respectively in both ends about, and left gear coupling connects to turn left in the left side wound packages and puts, and the gear coupling's on right side right side rises retarder connection through one nonstandard and turns right the wound packages and put, the right -hand member that the wound packages of turning right was put is connected one and is played to rise brake motor, the right side of playing to rise brake motor is provided with a manual release device, the left side that the wound packages that turns left was put is provided with an encoder and observes andcontrols the appearance with an aperture loading and is connected. This mechanical faults rate low, the vibration is little, safe and reliable, be convenient for open and close and overhaul and maintain anti -flooding protective airtight door.