Deep-water depth-keeping release lock and application method thereof in deep-water pipeline installation

The invention discloses a deep-water depth-keeping release lock. The deep-water depth-keeping release lock comprises an air inflation floating body and a padlock, and the air inflation floating body is used for wrapping a pipeline and the padlock is arranged at the periphery of the floating body and used for fastening the floating body; the padlock comprises a hasp and a lock bolt, the lock bolt and the hasp are fastened in a combination way; a spring is arranged on the hasp, a depth adjustment knob screw for adjusting the deformation quantity of the spring is arranged at one end of the spring, and the spring can push away the lock bolt in a set depth. The depth adjustment knob screw is arranged on the deep-water depth-keeping release lock, so that the system depth can be designed by an operator according to a construction region and the depth adjustment knob screw of the padlock can be set; the floating body and the padlock are set so that gas in the floating body is compressed along with change of water depth; the perimeter of the floating body is reduced, and the lock bolt is pushed away by the spring in the hasp, so that the padlock can automatically open. The deep-water depth-keeping release lock is applied to the marine engineering field.