The invention relates to recombinant protein of A1S_1523 as well as a preparation method and application of the recombinant protein. The recombinant protein comprises A1S_1523 mature peptide, and an amino acid sequence of the recombinant protein is shown in SEQ ID NO. 3. The recombinant protein disclosed by the invention is high in expression quantity and convenient to separate and purify, is efficient and safe, can be directly matched with adjuvants for use, and can be used for preparing acinetobacter baumannii infection resistant subunit vaccines and related detection kits; proven by animal experiments, gene engineering recombinant monovalent subunit vaccines have good immune protective effects on acinetobacter baumannii infection resistance; and the recombinant protein can be used for laying a foundation for further researching combined vaccines and multi-subunit fusion vaccines, and can also play important roles in the development and application of prevention and treatment vaccines and diagnostic kits.