Objective To explore the effect of Naja atra venom on blood coagulation in rats. Methods Whole blood was incubated with Naja atra venom or various fractions in vitro and a thromboelastogram was obtained. In an in vivo experiment, Naja atra venom was injected via the tail vein or intramuscularly and whole blood samples were collected at various time points to obtain the thromboelastogram. LDH, hemoglobin, vWF, and P-selectin were measured in plasma. The activity of coagulation-related enzymes in plasma was measured by the chromogenic substrate method. Results The in vitro and in vivo result showed that Naja atra venom and some of its fractions obviously induced an abnormality in the coagulation function in rats, which was characterized by a lack of coagulation factors, low level of fibrinogen, and lowering of the platelet count and function, while the plasma hemoglobin content and LDH activity were increased significantly. In vitro, Naja atra venom and its fractions significantly decreased the enzymatic activities of cleaving S2238 and S2251. In vivo, after intramuscular injection, the content of P-selectin was significantly increased at 30 min and the enzymatic activity of cleaving S2765 was significantly increased within 6 h. After tail vein injection, the enzymatic activity of cleaving S2238 was increased significantly within 2 h and vWF content was increased obviously within 6 h. Conclusions Naja atra venom induces an obvious abnormality in the blood coagulation function of rats. Its effect is mainly related to the consumption of coagulation factors and fibrinogen caused by activation of the coagulation system and the consumption of platelets.