Abstract: Objective: To screen the marine microbial antithrombotic strains from Naozhou island in South China Sea,and study its effects on blood coagulation characteristics.Methods: The antithrombotic strains were screened by in vitro thrombolysis,and the effects of the screened strains on collagen-adrenergic-induced tail vein thrombosis,bleeding time and clotting time of mice,and thrombin-induced platelet aggregation of pig were investigated.Results: The in vitro thrombolysis experiments showed that the Staphylococcus saprophyticus(Mb19) and Acetobacter pylori(Lmb14) had obvious thrombolytic effect.The high-dose of supernatants(1 mL) of Mb19 and Lmb14 could effectively inhibit the formation of collagen-adrenergic-induced thrombosis in mouse,and the difference between which and 0.9% sodium chloride injection was statistically significant(P<0.05).The high-dose of supernatants(1 mL) of Mb19 and Lmb14 could effectively prolong the bleeding and clotting time of mice,and the difference between which and 0.9% sodium chloride injection was statistically significant(P<0.01).The high-dose of supernatants(1 mL) could inhibit the platelet aggregation.Conclusions: Mb19 and Lmb14 marine bacteria have the activity of anti-thrombosis.