The invention discloses a nano-antibody for specifically recognizing duck hepatitis A virus 1. The amino acid sequence of the nano-antibody is represented by SEQ ID NO.1. The nano-antibody has the advantages of small molecular weight, high stability, excellent antigen binding performance and easy expression, and provides a basis for the detection of the duck hepatitis A virus 1 and the developmentof treatment medicines. A mutant with good endophilicity, specificity and stability can be obtained through reconstructing by using a random or site-directed mutagenesis technology with the nano-antibody as a precursor, and is used for developing proteins or polypeptides for being further used in medicines, industries and agriculture.