The invention relates to a pipe string of an oil-gas development well completion and well cementation process, in particular to a pipe column structure of a multilateral well window upper tie-back well cementation process. A sealing section in tie-back sealing connection with a multilateral well window upper tie-back cylinder is arranged on a tie-back head of the structure; the upper end of the tie-back head is in screwed connection with an anti-dropping cylinder; a hole for communicating upper pressure with lower pressure is formed in the anti-dropping hole; the upper part of the anti-dropping cylinder is in screwed connection with a drillable one-way valve; when the lower pressure of the drillable one-way valve is higher than the upper pressure of the drillable one-way valve, the drillable one-way valve is upwards opened; the upper part of the drillable one-way valve is connected with well cementation accessories; and the well cementation accessories comprise a cement injecting grading hoop and an annular packer. The structure realizes the release of trap pressure in the tie-back of a pipe column, guarantees the tie-back of the pipe column in place, prevents well cementation cement from settling to a window to influence the window cut-through, prevents the upper well cementation accessories from dropping into a lower multilateral well shaft in drilling to influence the subsequent construction, and guarantees smooth implementation of the multilateral well window upper well cementation process.