The invention relates to gene segments for coding alpha, beta or gamma interferons of pigs and an application thereof. According to the preference of codons of a Pichia stipitis expression system, high-expression codons are selected to renewedly design and synthesize new mature peptide nucleotide sequences of the alpha, beta and gamma interferon of the pigs, and recombinant yeast expression plasmids of pPICZalphaC-IFN-alpha, pPICZalphaC-IFN-beta and pPICZaplhaC-IFN-gamma are successfully constructed, which not only correctly expresses the alpha, beta and gamma interferons of the pigs in Pichia stipitis, but also enables the alpha, beta and gamma interferons of the pigs to be easier to express in the Pichia stipitis with higher expression level, and lays a foundation for the large-scale production and fermentation of the gene engineering.