Reef-building coral, as a biological carbonate and the main body of coral reef ecosystems, is sensitive to environmental changes, has a clear annual growth layer of aragonite skeleton, a large annual growth rate, is easy to date accurately, and can record changes in their growth environment reliably; hence, it is considered an essential carrier for studying environmental changes. Coral has been degraded worldwide in recent decades due to human overexploitation of the coast. Nitrogen is one of the major nutritional elements used to understand coral growth. Nitrogen isotopes can reflect variations in nitrogen sources and biogeochemical cycles, such as recording nearshore nitrogen loading and nitrogen cycles. Many studies on nitrogen isotopes in coral skeletons have been published worldwide; however, relevant reviews are still lacking. In this study, we focused on coral nitrogen source tracing, the nitrogen cycle, and nitrogen isotope analysis. Currently, most studies have been conducted on the history of variations in coral nitrogen sources and have mainly focused on the impact of human activities on coral ecosystems. In the future, coral skeleton δ¹⁵N should be utilized to conduct more research on coral skeleton δ¹⁵N in different seas and at different time scales and to explore new analytical techniques to distinguish the overlap of physiological and environmental signals in combination with other geochemical indicators, which is of great significance for the reconstruction of the paleoceanographic environment and research on current environmental pollution problems.