Uncontrolled bleeding following trauma is associated with a high risk of death. Here, an emerging kaolinite nanoclay composite (iron oxide-kaolinite, α-Fe 2 O 3 -kaolin KAc ) is developed, based on the natural hemostat hematitum used in traditional Chinese medicine to effectively control hemorrhage. α-Fe 2 O 3 -kaolin KAc stops bleeding in ≈183 ± 16 s and exhibits higher hemostatic activity than the related compounds FeOOH-kaolin KAc (298 ± 14 s), γ-Fe 2 O 3 -kaolin KAc (212 ± 11 s), and Fe 3 O 4 -kaolin KAc (218 ± 15 s). This rapid effect is attributed to efficient absorption of the fluid in blood, activation of blood platelets, and induction of the coagulation cascade by kaolinite and the aggregation of red blood cells induced by α-Fe 2 O 3 . α-Fe 2 O 3 -kaolin KAc shows slight hemolysis (<0.11%) as compared to kaolinite (30%), which accelerates wound healing. The biocompatibility, hemostatic activity, and low cost of α-Fe 2 O 3 -kaolin KAc make it a safe and effective agent for preventing massive blood loss after traumatic injury.