Tail pipe head leakage well secondary well completion pipe string and well completion method

The invention relates to a drilling liner head leakage well secondary well completion method which is applied to the field of oil and gas drilling well completion and well repair. The device is composed of an expansion cone, an expansion hanger, a sealing hanging element, an expansion cone bearing shaft, a salvage type sealing plug, an outlet falling object preventing device, a center pipe, a tail pipe sealing back-inserting connector and the like. After a system is lowered to a preset position and a tail pipe sealing back-inserting connector is inserted into a tie-back barrel of an original well hanger, an expansion cone axially slides in the expansion hanger along a central pipe in a hydraulic or hydraulic and mechanical combined mode, so that an expansion hanger body generates permanent plastic deformation in the radial direction; and the rubber element on the expansion hanger is compressed in an annular space between the expansion hanger body and the outer-layer sleeve, so that the purposes of sitting han