The invention discloses the application of protein MUC13 in the preparation of reagents for diagnosing intrahepatic cholangiocarcinoma. The present invention utilizes the advantages of high-throughput and rapid analysis of the human proteome chip to analyze the relevant serum of patients with intrahepatic cholangiocarcinoma, compare the differences between the samples of intrahepatic cholangiocarcinoma patients and healthy people in a short period of time, and find that the MUC13 protein The expression level of MUC13 in patients with intrahepatic cholangiocarcinoma was significantly higher than that in healthy people, suggesting that MUC13 protein can be used as a candidate serum biomarker for intrahepatic cholangiocarcinoma for early diagnosis and effective treatment of intrahepatic cholangiocarcinoma. Tests have proved that the serum marker MUC13 provided by the present invention has a specificity of 90%, a sensitivity of 91.67%, and has the characteristics of high specificity and high sensitivity. Further, the present invention also provides a sensitive, safe, reliable, and easy-to-operate commercial kit, which can be used to qualitatively measure the level of anti-MUC13 IgG antibody in human serum, which is helpful for the early diagnosis of intrahepatic cholangiocarcinoma.