The invention belongs to the fields of biomedicine and molecular biology, and relates to a new diagnostic marker for biliary atresia. Specifically, the application of a group of microRNAs in the preparation of biliary atresia diagnostic preparations is provided, and the microRNAs are composed of hsa-miR-150, hsa-miR-4689, hsa-miR-92a-3p and hsa-miR-4429. Experiments have shown that in the serum of biliary atresia, there is a statistically significant difference in the expression levels of the above miRNAs and the corresponding miRNAs of cholestatic infantile hepatitis syndrome. The present invention also provides a detection method for this group of miRNAs, which saves time, has higher sensitivity and accuracy, lower cost, and / or is more efficient than prior art detection. In addition, the present invention also provides kits and chips related to these applications.