Serum amyloid A(SAA) is a novel marker widely used in the acute infection disease, especially viral infection. SAA has shown a cerntain value in assisting the clinical diagnosis, discrimination of severity and monitoring of progress and outcome of COVID-19. This paper introduces the application of SAA structural, function andits dynamic detection in the diagnosis of COVID-19, and the significance of combined detection with COVID-19 antibodies, nucleic acid and other diagnostic indicators.