Underwater drilling construction method of drilling ship

The underwater drilling construction method of the drilling ship comprises the steps of construction preparation, measurement and positioning, installation and debugging of a drilling machine anchor gear, manufacturing of an anchoring point, installation of a mooring device, hole location positioning and vertical guide drilling. During hole location positioning, a transverse cable is hung on the preset anchoring point through an anchor boat. An anchor cable is controlled through the electronic lofting graph to enable the ship to move to the position near the position needing to be drilled, and the ship is stopped to throw a rear main anchor; seven anchor cables are arranged, and the ship is commanded to move to enable the drilling position of the drilling machine to coincide with the designed hole position; during vertical guide drilling, a casing vertical guide system is started, an upper guide disc and a lower guide disc of the casing vertical guide system hold a casing respectively, and the holding force o