Abstract: With the proposal of China's "dual carbon" goal and the focus of upgrading the water treatment industry to biological nitrogen removal, sewage treatment plants have shifted from focusing on meeting emission permit limits to realizing carbon neutrality, energy self-sufficiency and resource recovery potential. Anaerobic ammonia oxidation (Anammox) technology, with the advantages of no additional organic carbon source, small footprint, small sludge production and high nitrogen removal efficiency, represents the future development direction of biological nitrogen removal in sewage, with energy saving, consumption reduction and carbon emission reduction. Based on the existing research results, the discovery history of traditional nitrogen removal and Anammox reaction was summarized and compared. The application progress of emerging partial nitrification and Anammox (PN-A), partial denitrification and Anammox (PD-A), and anaerobic methane denitrification and Anammox (DAMO-Anammox) processes in urban mainstream conditions were reviewed. The endogenous and exogenous regulation strategies and their internal mechanisms, which could be implemented when the mainstream Anammox process was confronted with environmental factors such as low temperature, uneven influent load and light, were explored in detail. These strategies include "side-flow sludge supplement to mainstream" "side-flow sewage intermittent supplement to mainstream" and "acclimated biofilm particles", and so so on. Finally, future directions for accelerating the innovative development and application of Anammox nitrogen removal technology were proposed in terms of molecular biology technology, material sciences, digital information technology, and management policies.