Female, 50 years old, has had recurrent abnormal liver function ALT for many years, with occasional mild abnormalities of ALP, repeated negative autoimmune antibody tests, and normal immunoglobulins. Routine viral hepatitis and non-hepatophilic viral tests were negative. Liver function was normalized by treatment with glycopyrrolate and other agents, but the disease was recurrent. Histological examination of the liver: moderate to severe interface inflammation involving multiple confluent areas, lymphocytic infiltration predominant, a small number of plasma cells, balloon-like cellular degeneration edema, interlobular bile duct damage, bile duct reactions evident, rose node-like hyperplasia cells visible, lymphocyte penetration phenomenon visible, confluent areas enlarged, bridging-like fibrosis formation. The diagnosis of autoimmune hepatitis was made. The disease was rapidly controlled with hormone therapy. Diagnosis and treatment experience: Serum autoantibodies are one of the immunological features of AIH. About 10% of AIH patients are negative for routine autoantibodies, and the serum IgG level is often elevated to a lesser extent or even normal in these patients, which makes the diagnosis of AIH very difficult. Therefore, liver biopsy is strongly recommended for definitive diagnosis in suspected autoantibody-negative AIH, and sometimes liver histologic manifestations are the only basis for its definitive diagnosis. These patients can be treated with glucocorticoid monotherapy or combination therapy, and the response to immunosuppressive therapy is often similar to that of typical AIH, and the effectiveness of such drug therapy is also strong evidence for the diagnosis of AIH.