Objective To explore the diagnosis and treatment measures,causes of misdiagnosis,and preventive measures for autoimmune hepatitis(AIH).Methods The clinical data of 21 patients with AIH misdiagnosed as viral hepati-tis admitted to our hospital from January 2020 to May 2022 were retrospectively analyzed.Results All the 21 patients had main symptoms,such as anorexia,fatigue,jaundice and fever,accompanied by abdominal distension(n =12),nausea(n = 5),chest tightness and chest pain(n =4),vomiting(n =3),arthralgia(n =3),wasting,and obvious yellowing of sclera and skin mucosa.Serum alanine aminotransferase and aspartate aminotransferase were detected to be increased.γ-glutamyl transpeptidase was increased in 7 patients,and alkaline phosphatase and total bilirubin were increased in 6 patients.Abdomi-nal B ultrasonography showed enlarged liver in 18 cases with uneven liver echo.Initial diagnosis of viral hepatitis in other hos-pitals,and patients did not respond to 15-day symptomatic treatment,and then transferred to our hospital.The blood anti-smooth muscle antibody(SMA)and anti-nuclear antibody(ANA)were positive,and the blood γ-globulin and IgG were ele-vated.Based on the combined hepatitis virus serology testing that was negative,and related history,AIH was confirmed.Mis-diagnosis lasted 18 to 21 days.After diagnosis,18 patients were treated with Prednisone alone,and 3 patients were treated with Prednisone combined with Azathioprine.After 1-year follow-up,patients had stable condition without recurrence.Con-clusion The onset of AIH is relatively hidden,with a high incidence in young women,and the clinical manifestations are varied and non-specific,which is,therefore,more likely to be misdiagnosed as viral hepatitis.It can be distinguished by se-rology testing examination of hepatitis virus and ANA,SMA,anti-liver/kidney microsome,AMA,immunoglobulin or patho-logical examination of the liver tissue.After diagnosis,timely and effective treatment should be given to improve the prognosis of patients.