Hydrogen liquefaction system

The invention discloses a hydrogen liquefaction system. The system comprises a PLC main control module, a vacuum module, an impurity analysis module, a helium compressor module, an upper computer module, a cold box, an oil removal module, a gas management module, a water chilling unit module, a gas distribution module, a nitrogen and liquid nitrogen supply module and a cold trap module; Modules, with the IO point position number smaller than a set threshold value, in the vacuum module, the impurity analysis module, the helium compressor module, the cold box, the oil removal module, the gas management module, the water chilling unit module, the gas distribution module, the nitrogen and liquid nitrogen supply module and the cold trap module are connected with the PLC main control module through signal lines; and the modules with the IO point position number larger than the set threshold value are connected with the PLC main control module through a switch, and the PLC main control module controls operation of t