Objective: To investigate the activity of coagulation and fibrinolysis systems in bronchoalveolar lavage fluid (BALF) in lung fibrosis in rats, and to study their role in diagnosis of lung fibrosis. Methods: Thirty-six Sprague-Dawley rats were randomly divided into 2 groups (n=18 in each group ). Lung fibrosis and control models were made by tracheal instillation bleomycinA_5 (BLMA_5) (5 mg/kg) and saline. On days 7, 14 and 28, the recalcification time points of normal pooled plasma for studying procoagulation activity (PCA), the levels of von Willebrand Factor (vWF), the activities of Antithrombin-Ⅲ(AT-Ⅲ) , plasminogen activity inhibitor-1 (PAI-1) and urokanise-type plasminogen activator(uPA) in BALF were measured respectively. Results: (1) In BLM group,the recalcification time points in BALF were (56?10), (78?3) and (172?11) seconds respectively, they were (190?10), (186?8) and (184?6) seconds respectively in control group. The difference was significant(P