The phase transition process during the hydrogen reduction of ironsands remains unclear. One of the primary objectives of this chapter is to elucidate the phase transitions occurring during the reduction process, with a focus on reaction time and solid solubility. Furthermore, the experimental parameters of temperature and hydrogen concentration are systematically varied to investigate their effects on the reduction mechanism of ironsands. This approach aims to identify reduction parameters that optimize both reaction rate and economic feasibility. Finally, the microscopic morphology of ironsands during the hydrogen reduction process is presented, and three distinct reduction pathways characterized by different morphological features are summarized.