The invention discloses a fusion protein consisting of sheep interleukin 2, sheep interferon gamma and sheep interferon tau and a preparation method thereof. The fusion protein is formed by connectingthe sheep interleukin 2, sheep interferon gamma and sheep interferon tau through a flexible linker, and a recombinant sheep long-acting interferon can be obtained through freeze drying after the fusion protein is compounded with a freeze-drying protective additive. The recombinant sheep long-acting interferon can obviously improve the half-life period of the sheep interferon, the half-life periodof the sheep interferon is prolonged by more than 17 times by compared with that of common sheep interferon, the fusion protein has a broad-spectrum antiviral role, and the immune response of sheep can be improved.