Since the steam turbine plant has the flexibility of fuel selection [oil only, gas only or dual] so most propulsion plants for Liquid Natural Gas (LNG) Carriers have been up till now, steam turbine. However, what with the rising prices of fuel and the shortage of steam turbine engine room crew, investigation into a higher efficiency propulsion plant has been growing. Actually, a lot of LNG carriers, for European owners, have adopted a dual fuel diesel engine plant with an electric propulsion motor (DFE) . Many large size LNG carriers (200, 000 m3) being built in Korean shipyards have recently adopted a diesel engine plant with a re-liquefaction system (DRL) . Under these circumstances we propose a new high efficiency plant. The Ultra Steam Turbine (UST) plant offers advantages over conventional steam turbines; high reliability, safety, low maintenance cost and easy operation. The restitution of the steam turbine plant contributes to the recovery of market share and the exploitation of new markets. In this paper we introduce the outline, features and key technology about the development of the reheat boiler, that which is one of main components of the UST plant.