Abstract: The present disclosure provides use of a reagent for detecting an expression level of transferrin in the preparation of a diagnostic reagent or kit for a disease caused by imbalance of intestinal immune tolerance, and belongs to the technical field of medical molecular biology. In the present disclosure, the severity of intestinal inflammatory diseases is diagnosed according to the transferrin level, achieving the objective of the early diagnosis of the disease caused by imbalance of intestinal immune tolerance. In the present disclosure, the transferrin is used as a marker for imbalance of intestinal immune tolerance, featuring high specificity and sensitivity, and simple detection procedure.