Typical acute nephritis is not difficult to diagnose. After 1 to 3 weeks of asymptomatic interval after streptococcal infection, edema, hypertension and hematuria appear . In the acute phase, there is mostly an increase in the potency of anti-streptococcal hemolysin “0”, a decrease in serum complement concentration, and an increase in urinary FDP content, which is more helpful for diagnosis. Individual patients have acute congestive heart failure or hypertensive encephalopathy as the initial symptoms, or the beginning of the disease only edema and hypertension and only minor or no urinary routine changes, for atypical cases should be detailed medical history, systematic examination combined with laboratory analysis, in order to avoid misdiagnosis, for clinical diagnostic difficulties, if necessary to do renal biopsy to confirm the diagnosis. Diagnostic basis 1. History of streptococcal infection is obvious before the disease Clinical symptoms of acute nephritis such as hematuria, proteinuria, oliguria, edema and hypertension are typical. 2.Streptococcal culture and serological examination The diagnosis of the disease can be confirmed by positive culture of pharyngeal or skin pus crust secretion showing group A hemolytic streptococci, decreased serum complement and increased serum ASO. In case of atypical clinical manifestations, the diagnosis should be made based on urine examination and dynamic changes in serum complement. Because 90% of glomerulonephritis after acute streptococcal infection have hypocomplementemia, serum complement determination can be used as the first-line test to evaluate acute nephritis. 3, laboratory tests: ① urine routine is dominated by red blood cells, and there may be mild or moderate protein or granular tubularity. ②Blood urea nitrogen may be temporarily elevated in the oliguric phase. ③Blood sedimentation is increased in the acute stage. The potency of anti-O is increased, mostly above 1:400. ④Serum complement C3 measurement decreases significantly at the onset of disease >2 weeks and returns to normal in 6-8 weeks. 4. Other tests Usually, renal biopsy is not required in typical cases, but it is required if there is difficulty in differentiating from acute nephritis; or if there is still hypertension, persistent hypocomplementemia or renal function impairment 3 months after the disease.