The invention belongs to the field of hydrate resource development, and provides a mining device of seabed shallow surface blocky hydrates, and a pressure-maintaining drilling and recovering method inorder to solve the problem that a shallow surface hydrate reservoir solid state mining method is poor in operability. The mining device comprises a seaborne mining ship and an underwater submarine mining device; the underwater submarine mining device comprises a submarine drilling machine, a pressure-maintaining core seat frame, a submarine underwater robot, a mining ship and a submarine excavating engineering van; and the submarine drilling machine comprises a drilling machine rack, and the drilling machine rack is internally provided with a submarine drilling machine control system, a drilling machine drilling mechanism and a core placement platform. The pressure-maintaining drilling and recovering method adopts the mining device and comprises the following steps: stripping of settlingscovering the seabed shallow surface hydrates; and drilling and transferring of the seabed shallow surface blocky hydrates. The sea surface mining ship controls the submarine mining device to drill and transfer the seabed shallow surface blocky hydrates, and recovered pressure-maintaining hydrate cores are preserved and transported through the mining ship.