Serum amyloid A protein (SAA) is an acute phase responsive protein belonging to the heterologous protein family of apolipoprotein, with a relative molecular weight of approximately 12000. A particularly important characteristic of serum amyloid A is that its degradation products can deposit in different organs in the form of amyloid A (AA) fibrils, which is a serious complication in chronic inflammatory diseases. The average serum SAA concentration in normal individuals is 2.33mg/L, and the determination of SAA concentration is more sensitive for the diagnosis of acute rejection in kidney transplantation than serum Cr. In the absence of infection, abnormal elevation of SAA has great diagnostic value for acute rejection in kidney transplantation. Similar to C-reactive protein (CRP), the concentration of serum amyloid A is a sensitive indicator of early inflammation of infectious diseases, which is helpful to diagnose inflammation, evaluate its activity, monitor its activity and treat it. However, serum amyloid A testing is more accurate than C-reactive protein in diagnosing patients with viral infection, kidney transplant rejection (especially those undergoing immunosuppressive therapy), and cystic fibrosis treated with corticosteroids. Research has found that in cases of inflammatory arthritis, serum amyloid A is most closely related to disease activity. Simultaneously detecting C-reactive protein and serum amyloid A can improve the diagnostic sensitivity for infections. For patients with amyloid A amyloidosis, treatment aimed at restoring serum amyloid A levels to normal can improve the condition.