The invention discloses an underwater constructed water sealing layer monitoring device for a vertical shaft. The underwater constructed water sealing layer monitoring device comprises a plurality oflifting devices, a water level monitoring device, a grout sampling device and a deep well imager, the water level monitoring device comprises a multimeter, a wire, an insulation board and an electrodetip, the electrode tip is installed on the insulation board, one end of the wire penetrates through the insulation board and is connected with the electrode tip, and the other end of the wire is connected with the multimeter; and the grout sampling device comprises a tube body, a grout inlet port and a sealing plate, the grout inlet port is formed in the side wall of the tube body, the sealing plate is connected with the tube body, and the multiple lifting devices are connected with the deep well imager and the tube body correspondingly. Through the structure, the conditions of the grout height change in a wellbore, the rising height change of the water level, the grout change along with the filling amount and the like are monitored in the whole process, the one-time success rate of constructing a water sealing layer through grouting is ensured, and the reliability of constructing the water sealing layer is improved.