The invention relates to a dock of sink-float chamber type, which comprises work bench (6) and air cavity located on the floor of workbench. Said air cavity comprises annular enclosed air cavity set on the perimeter of floor of work bench and variable air cavity with open structure at the bottom which comprises inner surface (3) of annular enclosed air cavity and the floor of workbench. Said variable air cavity (4) connects with air supply via air supply duct. On perimeter of the top side of work bench (6), many upright pontoons are set to keep balance. The invention has the properties of rational structure, low building cost of projects, movable property, simplicity of operation, safe reliability, no hull damage and low amount of maintenance work.