This document specifies evaluation methods of characteristics such as pressure, flow rate, temperature and system stability of fuel gas supply systems (FGSS), which are manufactured to use vaporized liquefied natural gas (LNG) or boil-off gas as fuel gas supply to the vessel's gas consumers. It is applicable to evaluate the performance of the LNG FGSS: (1) prior to delivery or after installation on board a ship, and (2) to assure the system characteristics are taken into account for the entire gas consumers during ship’s gas trial or sea trial.