Floating wind turbine facilities, which are installed in the deep sea area, play an essential role to promote the green energy application. One of the problems associated with the commercialization of facilities installed in the deep sea is the reduction of the maintenance cost of mooring chain. Therefore, it is necessary to establish a quantitative wear evaluation method for mooring chains. Specific wear is one of the essential physical parameter to evaluate the wear performance of metals. However, detailed investigation of the specific wear of the mooring chain has not been performed yet. The pin-on-disk wear tests were performed to measure the specific wear in the air and in the substitute ocean water. As a result of experiments, it has been confirmed that the specific wear in the substitute ocean water was remarkably smaller than in the air, and the wear state was stable.