One of the necessary conditions for a high speed ship is that a propulsive plant with big power has smaller size and lighter weight. When we plan a displacement-type monohull high speed ship, in particular, it is difficult to get the hull form with the wave-making resistance minimum, because the stern shape is limited by an arrangement of propulsive machines and shafts. If we have a small-sized and light-weight propulsive machines, we will expand the limit of hull form design. Superconducting technology will have capability of realizing the small-sized and light-weight propulsion motor. In this paper, we generally describe superconducting ship propulsion systems, and report the test results of the 480 kW superconducting motor which we have constructed for the purpose of developing superconducting electric propulsion system. Showing the design of a 150, 000200, 000 PS propulsive plant for a displacement-type monohull high speed ship, we discuss the possibility of the plant realizing, and pick up the subject for a future study.