Objective: To investigate the value of Antithrombin III (ATIII) activity in the evaluation of bleeding risk in patients with orthopaedic trauma. Methods: 62 patients admitted to the orthopaedic Trauma Center of our hospital from November 2022 to December 2024 were selected as the study objects. Patients were divided into control group (non-bleeding group) and study group (bleeding group) according to whether clinically significant traumatic bleeding occurred within 24 hours after admission. Baseline data were collected and compared between the two groups. The laboratory data of the two groups were detected and compared. t test, χ2 test and Mann-Whitney U test were used to compare the groups, Spearman correlation analysis was used to evaluate the correlation, Logistic regression analysis was used to screen independent risk factors, and receiver operating characteristic (ROC) curve analysis was used to evaluate the value of ATIII activity in predicting bleeding. Results: Among 62 orthopedic trauma patients, 19 cases of hemorrhage were included in the bleeding group (study group). A total of 43 patients without bleeding were included in the non-bleeding group (control group). In blood group, ISS score was significantly higher than that in non-bleeding group, ATIII activity was significantly lower than that in non-bleeding group, PT and APTT were significantly prolonged, FIB levels were significantly decreased, D-dimer levels were significantly increased (P <0.001), HGB and PLT were significantly decreased (P <0.05). Multivariate Logistic regression analysis showed that decreased ATIII activity, increased ISS score, and increased D-dimer were independent risk factors for bleeding in orthopedic trauma patients. ROC curve analysis showed that the area under the curve (AUC) of ATIII activity to predict bleeding was 0.920 (95%CI: 0.858-0.982, P<0.001), the best cutoff value was 74.90%, the sensitivity was 89.47%, and the specificity was 83.72%. Conclusion: Decreased ATIII activity is an independent risk factor for hemorrhage in orthopedic trauma patients, and has good predictive value.