With the background of marine engineering emergency repair, the laser wire filling cladding experiment on Q345B low carbon steel plate was carried out by using hyperbaric welding test chamber to simulate water depth pressure under environmental pressures of 0.1 MPa, 0.2 MPa, and 0.3 MPa respectively. The laser cladding was compared and analyzed for exploring the feasibility of hyperbaric laser repair in 30 m water depth. The microstructure, chemical composition, and phase composition of the cladding layer were analyzed by optical microscope, XRD, and EDS. The hardness was tested by microhardness tester. The corrosion resistance of the cladding layer was studied by potentiodynamic polarization curve. The results show that the cladding layer is well formed under the pressure of 0.1 MPa, 0.2 MPa, and 0.3 MPa, and no obvious defects are found. The cladding layer is mainly composed of cladding zone, overlapping zone, phase transformation affected zone, fusion zone, and heat affected zone. The microstructure is mainly composed of ferrite, pearlite, and part of Widmanstatten structure. With the increase of environmental pressure, the size of ferrite and the number of Widmanstatten structure increases. With the influence of microstructure, the hardness variation trends are the same under the three environmental pressures, and the hardness of the cladding layer is better than that of the base metal. In 3.5% NaCl solution, the cladding layer exhibits obvious passivation behavior, and its corrosion resistance is better than that of the base metal. With the increase of environmental pressure, the corrosion resistance decreases. The experimental results show that laser wire filling cladding technology has good adaptability and feasibility for hyperbaric underwater repairment.