Anti-human serum albumin single-chain antibody and method for connecting polypeptide medicine with nitrogen terminal of antibody

The invention discloses an anti-human serum albumin single-chain antibody and a method for connecting polypeptide medicine with the nitrogen terminal of the antibody. A VL chain region has a complementary identification region (CDR) which has the following amino acid sequences of CDRs: N-SEQ-08 of CDR1, N-SEQ-09 of CDR2 and N-SEQ-010 of CDR3; a VH chain region has a complementary identification region which has the following amino acid sequences of CDRs: N-SEQ-05 of CDR1, N-SEQ-06 of CDR2 and N-SEQ-07 of CDR3; the VH chain takes the amino acid sequence shown as N-SEQ-02 as an expression form; the VH chain takes the amino acid sequence shown as N-SEQ-04 as an expression form; and the VH chain region and the VL chain region are connected through a protein hinge shown as N-SEQ-01 or N-SEQ-03. The single-chain antibody has small molecular weight, strong specificity, weak immunogenicity and high water solubility and is easily produced on a large scale in a fermentation mode. The invention also discloses a composition prepared from the single-chain antibody; and the medicine can effectively prolong the half-life period of polypeptide biological medicines.