The invention provides a submarine pipeline connection operation pipe segment axial alignment device, and is applied to the underwater alignment during pipe segment connection. The pipe segment axialalignment device adopts a full-symmetry structure, and achieves the axial alignment among submarine pipeline pipe segments on the basis of the quick clamping of a submarine pipeline clamping device, alignment positioning of a pipe segment aligning device, axial supporting of a pipe segment supporting device, two-way limitation of a lifting limiting device and propulsion power provided by a hydraulic cylinder jacking device and hydraulic cylinder circumference pushing device; the submarine pipeline clamping device adopts a horizontal-type shell body and achieves the underwater quick clamping between a front clamping body and a back clamping body and a submarine pipeline by depending on the hydraulic cylinder circumference pushing device; the pipe segment aligning device achieves the underwater alignment positioning of two pipe segments by taking a reference positioning action of an alignment substrate as a basis and combining a moving pair between an alignment cylinder and a supportingcylinder; the pipe segment supporting device achieves the underwater supporting of two pipe segments by taking the hydraulic cylinder jacking device as a basis and combing a lifting sliding way provided by the supporting cylinder; and the lifting limiting device achieves the two-way limit of the axial supporting of the pipe segment supporting device on the basis of upper-layer and lower-layer spacer pins.