Objective · To investigate the and clinical significance of α1-antitrypsin (α1-AT) in tears of thyroid-associated ophthalmopathy (TAO) patients. Methods · Patients diagnosed with TAO at Shanghai Ninth Peoples Hospital, Shanghai Jiao Tong University School of Medicine January to December 2019 were included and divided into active TAO group (n33) and inactive TAO group (n22). Thirty eyes of 30 healthy volunteers were included (n30). Unstimulated tear samples were collected all subjects and the concentration of α1-AT was analyzedenzyme-linked immunosorbent assay (ELISA). Difference of α1-AT concentration among 3 groups was comparedusing Kruskal-Wallis H test. Mann-Whitney U test was performed for further comparison between each 2 groups. Correlationship between α1-AT concentration and clinical activity score (CAS) was analyzedSpearman relation. Statistical significance was accepted at a value of PResults · α1-AT was significantly higher in active TAO group than that in inactive TAO group and control group (both Pr0.846, P0.000). ROC curve showed that the optimal diagnostic cut off value of α1-AT was 939.48 ng/mL, and the sensitivity and specificity were 81.8% and 100% (AUC0.959, PConclusion · α1-AT is significantly elevated in the tears of active TAO patients. Tear α1-AT level has important value in the diagnosis of clinical activity of TAO.