A variety of thermodynamic cycles for hydrogen liquefaction are presented as an initial effort of the newly launched governmental project to develop the core technologies for commercial hydrogen liquefaction plant. Hydrogen liquefaction is one of fully developed cryogenic technologies, especially for large-scale applications, such as the liquefaction rates of 1,000 L/h or greater. The standard hydrogen liquefaction plant is based on “open” Claude cycle, where hydrogen gas is the working fluid itself that experiences compression and expansion, and liquid nitrogen is used as optional pre-coolant. For smaller applications and under specified regional conditions, the standard thermodynamic structure can be modified in a number of different ways. One significant modification is to employ various helium Brayton refrigeration cycles with one or more units of turbo-expanders. Since the cold end temperature is lower than 20 K, the refrigeration cycle is in direct thermal contact with hydrogen stream from room temperature down to cryogenic liquid. Two or more expanders may be arranged in series or parallel in order to improve the thermodynamic efficiency. An important regional condition in Korea is to utilize the cold energy of LNG (liquefied natural gas) for pre-cooling of hydrogen liquefaction process, as LNG is a source of hydrogen production as well. After numerous possible combinations of thermodynamic structure are introduced, several suitable cycles for domestic development are selected and their expected performances are compared in terms of FOM (figure of merit), operating pressure and flow rate of refrigerant, and size of heat exchangers. Details of optimized cycles are demonstrated and discussed towards the immediate design of liquefaction process and the construction of pilot plant.