Abstract: Objective To evaluate the value of lacrimal gland herniation（LGH）in judging the activity of thyroid-associated ophthalmopathy（TAO）and predicting the efficacy of glucocorticoids. Methods A retrospective analysis was conducted on the clinical data of 238 patients with TAO who were hospitalized at the Department of Endocrinology and Metabolic Diseases,the Third Affiliated Hospital of Sun Yat-sen University,from January 2014 to November 2022. Magnetic resonance imaging（MRI）was used to measure LGH and its differences were compared among different activity groups. Spearman rank correlation analysis was used to assess the correlation between LGH and the clinical activity score（CAS）. The effectiveness of LGH in staging TAO activity was evaluated using the receiver operating characteristic（ROC）curve. Follow-up was performed on 92 patients receiving glucocorticoid therapy to analyze the differences in LGH between the different efficacy groups. The influencing factors of efficacy were analyzed by multivariate Logistic regression analysis. Results The LGH of patients in the active group was higher than that in the non-active group（P < 0.05）. Spearman rank correlation analysis results showed a positive correlation between LGH and CAS score（P < 0.05）. The ROC curve analysis showed that the staging efficacy of LGH for TAO activity was optimal when the cut-off value of LGH was 9.78 mm,with an area under the curve（AUC）of 0.703,sensitivity of 78.9%,and specificity of 54.8%. Combining external ocular muscle thickness（EOMT）with LGH further improved staging efficacy,with an AUC of 0.752,sensitivity of 62.7%,and specificity of 78.1%. The AUC for the combined EOMT and LGH was greater than that for LGH alone（Z = 2.052,P < 0.05）. In the glucocorticoid treatment efficacy group,LGH was lower than in the ineffective group（P < 0.05）. Multivariate Logistic regression analysis indicated that LGH was an independent predictor of efficacy（P < 0.05）. Conclusions The LGH of TAO patients is correlated with the CAS score and can be used as a good indicator to judge the activity of TAO. The combination of LGH and EOMT can effectively improve the staging efficacy of TAO,thus providing effective assistance for precise clinical diagnosis and treatment.