The invention relates to a hard multi-layer composite medical splint material and a preparation method thereof. The multi-layer composite medical splint material is formed by three layers, the innermost layer contains natural eucommia ulmoides rubber composite material, an antibacterial agent and a crosslinking agent; the intermediate layer contains a natural eucommia ulmoides rubber composite material, a foaming agent and a crosslinking agent; and the outermost layer contains natural eucommia ulmoides rubber composite material, titanium dioxide and a crosslinking agent. The multi-layer composite medical splint material has good antibacterial property and mechanical performance and can be widely applied to the manufacturing of medical splints.