Paleontological research in the Southern Ocean based on quantitative studies of diatoms has progressed rapidly during the last 20 years, particularly on the Last Glacial Maximum (LGM) and Holocene paleoenvironment. This review of diatom paleoceanography in the Southern Ocean starts with reconstructions of the sea-ice distribution and productivity during the LGM. Maximum winter sea-ice distribution at the LGM (concentration > 15%) extended in the Atlantic and Indian sector close to 47°S, and in the Pacific sector as far north as 57°S. On the other hand, summer sea-ice distribution at the LGM was close to the modern summer sea-ice distribution except for the Weddell Sea extending as far as 52°S. However, LGM summer sea-ice information is still rather limited. Primary productivity in the Southern Ocean is closely related to the seasonal sea-ice zone. Increasing primary production under the seasonal sea-ice zone during the last glacial is linked to higher iron input. Sea-ice plays an important role as an effective transporter of dust-borne iron, and enhances its bioavailability. Termination periods of the surface condition in the Southern Ocean are described in relation to mechanisms of sea-ice distribution changes and their causes. Sea-ice retreat during the deglacial period and sea-ice advance during Neoglaciation in the Southern Ocean basically depended on solar insolation changes. However, the timings of sea-ice distribution changes were differentiated in each region. The last section, including short-term climate oscillations and their mechanisms, are described. Abrupt variations of Holocene diatom changes as 200–300 year cycle fluctuations indicate rapid climate changes of the Southern Ocean, which were very closely correlated to the solar activity cycle.