〔Abstract〕 Objective To investigate the procoagulant properties of red blood cell microparticles(RMPs) and the relationship between this property and acute lung injury in mice. Methods RMPs were isolated, purified and counted,and then the contents of the activated partial prothrombin time(APTT), prothrombin time(PT) and thrombin generation test were detected in the plasma of red cell supernatant under the circumstances before and after the removal of the microparticles and different concentrations of RMPs. In animal experiments,the levels of thrombin-antithrombin complex, plasminogen and plasminogen activator inhibitor-1 in mouse alveolar lavage fluid were measured by ELISA.Histological observation of right lung tissue in the experimental group injected with 3×107RMPs and the control group was conducted. Results The number of RMPs increased gradually with the prolongation of storage time.As the concentration of RMPs added increased, the APTT value of the degranulated plasma decreased slightly, while the PT value did not change significantly.When erythrocyte supernatant and RMPs with a certain range of concentrations were added to the plasma, the lag time and tt-peak could be shortened to some extent, while the peak and ETP were increased significantly with a concentration dependent manner. Compared with the control group, the TATc of BALF was significantly increased in the experimental group injected with 3×107RMPs, and the alveolar tissue inflammation was intensified and the coagulation promoting mechanism was enhanced. Conclusion As the storage time increases, the number of RMPs increases significantly. RMPs can promote thrombin generation and thereby promote systemic coagulation, which may be related to the transfusion-related acute lung injury(TRALI).