Abstract: The iron and steel industry is one of the major source of carbon emissions, and advancing pellet technology is one of the effective measures to achieve the "dual-carbon" goals. Excessive reduction swelling of pellets can degrade reactor permeability and even leads to production accidents. This paper systematically reviews the primary mechanisms of reduction swelling in iron ore pellets, including lattice expansion from phase transformations, iron layer cracking due to gas pressure, structural damage induced by carbon deposition, cracking resulting from uneven reduction stresses, and the precipitation morphology of nascent iron. Studies have shown that regulating the formation of iron whiskers is a key breakthrough in inhibiting malignant expansion, while reduction swelling is significantly influenced by preheating/roasting parameters, porosity, gangue composition, and reduction conditions. Key measures to suppress pellet swelling involve optimizing ore blending, rational control of basicity, refining preheating/roasting processes, and restricting harmful element intake. It provides a theoretical foundations and technical pathways for optimizing pellet performance and advancing low-carbon ironmaking technologies.