The 70th MEPC held in IMO on October 2016 decided that ship's fuel oil which contains sulfur under 0.5% can be used only from 2020. Heavy fuel oil included over 0.5% sulfur will not be able to use ship's fuel. Due to this reason, alternative fuels, such as low sulfur fuel, MDO, MGO, LNG, Methanol etc, are suggested. Especially LNG is being evaluated as the most suitable alternative fuel because of its economic feasibility and effectiveness of reducing emissions. So an increase in order for engines which use LNG and LNG supply facilities is expected. But there is lack of accumulated experiences about high pressure LNG fuel supply system, because it is a system developed recently. Therefore, LNG fuel supply system was designed and studied by process design system software. Because LP pump product pressure is difficult optimized pressure to define. In this paper, conduct an experiment by LNG fuel supply system test facility about optimized LP pump product pressure. Also, it is important that cooling LNG fuel supply system down under specific degree before operation because LNG fuel supply system applied cryogenic fluid. However, there is difficulty of defining optimal cool down temperature. So optimal cool down temperature was defined by process simulation software. Recently, imperfection of high pressure LNG fuel supply system stood out, one of them is pulsation of discharge pressure. The purpose of this thesis is to study pulsation of LNG fuel supply system by experiment, and suggest improved operation method.