The invention discloses a cat alpha and encoding gene and application, which comprises the following steps: possessing one of amino acid residue sequence proteins: (1) SEQ ID No.:2 in the sequence table; (2) replacing and/or deleting and/or adding SEQ ID No.:2 in the sequence table amino acid residue sequence through one or several sequence table amino acid residue and proteins in related to plant difficulty resistant. The invention can be applied to prepare anti-infective of anticat leukovirus, cat HIV and dog fine virus. the invention can be used as preparing anti-infective of anticat leukovirus, cat HIV and dog fine virus.