Abstract: The cycling mechanisms of iron-bound phosphorus (Fe-P) in marine sediments are pivotal in regulating the long-term sequestration and remobilization of phosphorus, profoundly influencing marine primary productivity and global carbon-phosphorus-iron coupled cycles. Traditional paradigms regard Fe-P as an easily remobilized "temporary reservoir"; however, recent studies reveal that specific occurrence forms within Fe-P—particularly vivianite—can achieve stable burial under certain redox conditions, representing an underestimated yet significant phosphorus sink. This review systematically summarizes the cutting-edge advances in Fe-P transformation mechanisms, unveils how iron oxide-driven anaerobic oxidation of methane (Fe-AOM) directly promotes vivianite precipitation by generating Fe²⁺, and indicated that enhanced terrigenous iron input during glacial lowstand periods could facilitate vivianite formation in non-seep areas. Furthermore, this paper elucidates how sea-level fluctuation, sulfide competition, and global warming-induced expansion of hypoxia modulate the activation-reimmobilization equilibrium of Fe-P by altering sedimentary redox gradients and iron supply fluxes. In this review, we identified key challenges—including precise identification of Fe-P speciation, microbe-mineral interactions, and cascading effects of global change—that are critical for constructing more robust marine phosphorus cycle models. These advances shall have significant scientific implications for predicting coastal eutrophication trends and phosphorus-climate feedback mechanisms throughout Earth’s history.