With the increasing scarcity of fossil fuels and the escalating environmental pollution, there is an urgent need to explore alternative energy carriers that can swiftly replace traditional sources. Hydrogen energy, as a novel paradigm in modern energy systems, possesses attributes such as high efficiency, cleanliness, and sustainability and can serve as a pivotal zero-carbon energy source that has garnered widespread attention. Currently, numerous methods exist for hydrogen production. However, establishing large-scale, efficient, low-cost, and environmentally friendly techniques is fundamental to realizing a hydrogen-based economy in the future. Thermochemical cycle hydrogen production through closed chemical reaction cycles offers an immense potential for development by directly decomposing water into hydrogen using heat. This chapter presents the existing thermochemical cycles and clean hydrogen production technologies while summarizing evaluation criteria and research progress on current thermochemical cycles.