The present invention discloses an iron oxide/nanokaolin composite hemostatic agent and a preparation method thereof. The composite hemostatic agent is composed of nanokaolin and iron oxide, where the nanokaolin is used as a carrier, and the iron oxide is loaded on a surface of a nanokaolin flake. The composite hemostatic agent is obtained by a precipitation method. The composite hemostatic agent has the advantages of good hemostatic effect, rapid wound healing, no obvious cytotoxicity, no hemolysis, high biocompatibility, and the like.