The present invention provides a composite hemostatic agent containing iron oxide/nano-kaolin and a preparation method thereof. The composite hemostatic agent consists of nano-kaolin and an iron oxide, wherein the nano-kaolin is used as a carrier, and the iron oxide is loaded on a surface of a nano-kaolin sheet. The composite hemostatic agent is obtained by precipitation and has advantages of good hemostatic effect, fast wound healing, no significant cytotoxicity, no hemolysis, and good biocompatibility.