Abstract: By report a case in which the main symptom was cholestasis in an infant and the diagnosis of Alagille syndrome (ALGS) was made after a tortuous treatment process, so as to provide clinicians with experience in diagnosing this type of patient. The patient was a 1-year and 11-month-old male who was admitted to the hospital with "abnormal liver function found for more than 1 year". Physical examination showed a wide forehead, sunken eye sockets, wide eye spacing, a sharp chin, and a grade II systolic murmur in the pulmonary valve region. Biochemical findings showed abnormal liver function accompanied by significant elevation of total bile acids and γ-glutamyl transpeptidase. CT scan of the thoracic vertebrae showed sagittal vertebral fractures in the thoracic 3-7 vertebrae, and pulmonary arteriography showed pulmonary stenosis and genetic testing indicated a JAG1 mutation. Combining the patient's specific facial features, heart defects, spinal deformities, and bile stasis clinical symptoms, along with the genetic analysis results, the final diagnosis was confirmed as Alagille syndrome. Alagille syndrome is the most common cause of chronic cholestasis with phenotypic features and is a dominant inherited disease involving multiple systems. Most patients present with bile stasis as the main symptom within the first three months after birth. Alagille syndrome needs to be distinguished from various forms of cholestasis in infancy, and since biliary atresia requires early surgical treatment, most children with cholestasis as the main clinical manifestation are considered to have biliary atresia at an early stage and undergo a caesarean section. If Alagille syndrome is misdiagnosed as biliary atresia, and surgery may worsen the prognosis. Therefore, the biggest challenge in the early diagnosis of Alagille syndrome is how to distinguish it from biliary atresia. Therefore, physicians need to improve their knowledge of rare cholestatic liver disease in clinical practice to accurately identify rare cholestatic liver disease in the early stages of the disease, and improve improve their diagnosis and treatment levels.