Submarine pipeline flange underwater abutting joint installation method

The invention discloses a submarine pipeline flange underwater abutting joint installation method. A main flange connecting device is installed on the abutting joint end of a submarine pipeline A, an auxiliary flange connecting device is installed on the abutting joint end of a submarine pipeline B, the submarine pipeline A to be butted and the submarine pipeline B to be butted are connected together through the main flange connecting device and the auxiliary flange connecting device, the negative influence of the marine condition on underwater flange connection can be removed, the influence of ship shake on the movement of the submarine pipeline A and the submarine pipeline B can be removed, underwater adjusting steps of a diver can be reduced, the diver can adjust the positions of the submarine pipeline A and the submarine pipeline B conveniently, the underwater operation difficulty degree of the diver can be reduced, the underwater operation time of the diver can be shortened, the case that flanges get close to each other in an aligned manner can be ensured, the force applied to a gasket of each flange is consistent, uniform deformation is generated, and the leakproofness of the flanges can be improved. The flange connection quality can be improved, the operating time of the support ship can be saved, the construction period of the whole fleet can be shortened, the working efficiency is improved, and the installation cost is saved.