The ocean, as the largest active carbon reservoir in the Earth surface system, presents a huge potential for carbon sequestration. Owing to their unique physiological structure, widespread distribution, efficient carbon sequestration mechanisms, and strong proliferative capacity, diatoms contribute about 40% of ocean primary productivity and 40% of particulate organic carbon export, playing an important role in the marine biological carbon pump. These organisms exhibit robust carbon sequestration efficiency and exceptional adaptability through powerful CO2 concentrating mechanisms (CCMs) and efficient biophysical and biochemical carbon fixation processes. They also offer opportunities for Carbon Capture, Utilization, and Storage (CCUS), presenting innovative avenues for biological carbon sequestration technology. Identifying and cultivating fast-growing diatom species, optimizing growth conditions, and enhancing photosynthesis efficiency are critical aspects. Current research has employed indoor physiological experiments to decipher factors influencing their physiological activities and carbon sequestration efficiency and further assessed the response of diatoms to global change from the perspective of global biogeochemical cycling. This provides an important theoretical basis for evaluating diatom-mediated natural carbon sequestration and their artificial augmentation prospects. Envisioned as a “microbial carbon sequestration factory”, diatoms hold promise in maximizing carbon sequestration capabilities while generating commercially valuable products. If the cost of carbon sequestration can be effectively reduced, diatom-driven carbon sequestration will be a technologically sustainable solution to support the “Dual Carbon Plan” in the future.