Abstract: A caisson structure including enclosed well walls with internal surfaces and external surface placed opposite to the internal surfaces is provided. A plurality of frame beams are provided between the internal surfaces and mutually intersected in a horizontal plane and a vertical plane. A bottom frame beam is provided close to a lowest end of the well walls. The internal surfaces are provided with internal support blocks at a first height, and the external surfaces are provided with external support blocks at a second height, with the second height greater than the first height. A bottom surface of the bottom frame beam is a plane without cutting edges, and the lowest end of the well walls is formed with cutting edges having an inclined surface. A method of sinking the caisson structure into the ground exactly is also provided.