During the construction of gravity wharf, caisson may sink or slip into the water due to the miss operation or other uncontrollable factors, which will affect the smooth implementation of engineering and bring a huge loss. In practice, by patching the caisson with the prefabricated steel cover plate and pumping, the caisson floated off the water surface under the buoyance and the problem was solved. This paper gives a detailed description of the refloating construction, and summarizes the methods, experience and matters of attention when dealing with similar problems.