Abstract: Hydrogen is an important clean and carbon-free secondary energy carrier in the future due to its extensive source, clean and carbon free, which will play a significant role in the world energy pattern. Hydrogen cryogenic densification technology can greatly improve hydrogen storage density and effectively solve the problems in large-scale storage and transportation caused by the low density and low boiling point of hydrogen. The developments of two cryogenic hydrogen storage technologies, hydrogen liquefaction and cryo-compressed hydrogen, were reviewed in this paper. The performance and characteristics of various cryogenic densification processes were introduced and compared, and the future development directions were summarized, providing a reference for the development of hydrogen storage and transportation technologies. Hydrogen liquefaction can achieve high hydrogen storage density with low hydrogen storage pressure, which is one of the mainstream large-scale hydrogen storage and transportation method at present. Cryo-compressed hydrogen could also reach a high storage density near liquid hydrogen with advantages of low intrinsic energy consumption and free of ortho-to-para hydrogen conversion, which has great development potential. Besides, closed refrigeration cycles such as mixed-refrigerant J-T cycles can effectively replace liquid nitrogen in the precooling or cooling hydrogen, which can significantly reduce the energy consumption of hydrogen densification and is an important development trend of cryogenic hydrogen storage technologies.