The utility model discloses a horn mouth special for a marine module drilling rig, which comprises a reflow pipe, wherein a draining pipe is arranged at the side part of the reflow pipe; the lower end of the reflow pipe is connected with a reducer pipe through a flange with large size; the reducer pipe is connected with a connecting pipe through a pneumatic tyre union; the bottom end of the connecting pipe is connected with a blowout preventer connecting flange through a pneumatic tyre union; and a hinge is arranged on the flange with large size. According to the horn mouth, the connecting pipe is connected with the reducer pipe and the preventer connecting flange through the pneumatic tyre unions, so that the connecting pipe can be stretched according to the height of a casing head at a well mouth and the height of the horn mouth is easy for adjustment; meanwhile, the horn mouth is more convenient for disassembly and assembly, the operation steps are simplified, the workload is saved and the work efficiency is improved; and in addition, by adopting the flange with large size and the hinge, the steps of disassembling the connecting pipe of the horn mouth and placing the connecting pipe on the surface of the drilling jig during each operation are avoided, so that the space of an operating board is saved, the labor intensity is greatly reduced and the time and the efficiency for the drilling operation are improved.