The invention belongs to the technical field of precise optical element manufacture and particularly relates to a silicon-aluminum alloy/zirconium extreme ultraviolet multilayer film reflector and a preparation method thereof. The reflector comprises a substrate and a silicon-aluminum alloy/zirconium period multilayer film, and the silicon-aluminum alloy/zirconium period multilayer film is formed by depositing a silicon-aluminum alloy film layer and a zirconium film layer alternatively on the surface of the substrate. Compared with the existing Al-base multilayer films, the silicon-aluminum alloy/zirconium extreme ultraviolet multilayer film reflector adopts a silicon-aluminum alloy to replace pure silicon, wherein the chemical property and the physical property of the silicon-aluminum alloy are stable. Under the condition that the optical property of an aluminum material is not changed greatly, crystallization of an Al film layer is restrained, an interface of the multilayer film is improved, and reflecting rate is of the reflector is improved under the premise that high spectrum resolution is guaranteed. The silicon-aluminum alloy/zirconium extreme ultraviolet multilayer film reflector has the advantages that the reflector is good in film formation quality and easy to manufacture, the optical property meets requirements, and the like, and the reflector is applicable to an extreme ultraviolet optical system having high requirements for energy spectrum resolution and reflecting rate.