Being sensitive to surrounding environmental changes, reef corals have proved to be capable of recording such environmental information as temperature, salinity and pollution. Red tides, visible ‘blooms’of phytoplankton, badly affect reef ecosystems. During red tides, alkalinity (or pH value), dissolved oxygen and concentration of iron and manganese in sea water are abnormal. Furthermore, the algae accumulate in large quantities to discolor the water, shade submerged reefs, block the photosynthesis of zooxanthellae, the symbiosis algae in polyps, and cause oxygen depletion when dead algae begin to decompose. The changes may lead to the extensive death of reef. In theory, the reefs that survive the red tides can record these changes in water. We can analyze the geochemical changes in coral skeletons such as boron isotope and trace elements like iron and manganese and probe into characteristics of corals so as to investigate the historical red tides. At present, the researchers on the response of coral reef to red tides and the record of historical red tides in reef corals are only in the beginning stages. The combination of the mechanism, characteristics and ecological impacts of the red tides with the characteristics of corals can not only help the study of coral reef environment record but also open a new way to record historical red tides. 