Abstract:Microorganisms are the dominant players driving the nitrogen cycles in hot springs. Thus, exporing microbial community composition of nitrogen-related microorganisms and their ecological response to environmental factors are of important theoretical and practical value for the study of biogeochemical cycling of nitrogen, life evolution and bioremediation. This review focuses on the distribution of functional microorganisms involved in the nitrogen cyclings and how their functional gene abundance and activity responded to environmental factors (e.g., temperature, pH). So far, microbial functional groups that have been investigated in hot springs included nitrogen-fixation, aerobic (anaerobic) ammonia oxidation and denitrification. Finally, prospect was given on the microbial studies on nitrogen cycles in hot springs.