A tube well and technologies for drainage, pressure reduction and dewatering pertain to the technical field of construction; the technical problem, the process optimization of the well points of a deep well dewatering function, is required to be solved; the tube well comprises a well pipe, a top-to-down vacuum pump, a filtering pipe, a submerged pump lower than the bottom of a foundation pit in the tube well, a top-to-down water-resisting clay for hole sealing, filter materials and water-resisting clay and filer materials lower than the foundation pit bottom outside the tube well, the invention also comprises a tube well water stopper inside the well pipe and below the submerged pump which meets the depth requirements of the submerged pump, matches with the diameter of the tube well and has the functions of easy adjustment and setting of depth and flexible water interception effect response. At the stage of drainage and dewatering stage, the water interception function of the water stopper is activated to facilitate the drainage and dewatering; and at the pressure reduction and dewatering stage, the water interception function is removed to realize the pressure reduction and dewatering of a confined aquifer. The invention has the advantages of lowing project cost, saving resources, accelerating construction progress, facilitating inside foundation pit operation, safe construction and easy operation.