Re-engineering mediated site-directed mutagenesis method

The invention relates to a site-directed mutagenesis method based on re-engineering. Firstly, a downstream segment, another resistant gene and a DNA (deoxyribose nucleic acid) modification segment are obtained by the aid of overlap-extension polymerase chain reaction, the downstream segment contains a left-end 50bp homologous arm, a mutagenesis site and a target gene mutagenesis site, the left-end 50bp homologous arm is consistent with an upstream 50bp sequence of a target site to be mutated, the target site to be mutated is cloned on a plasmid, the another resistant gene contains a resistant gene different from that of the plasmid, and the DNA modification segment with a right-end 50bp homologous arm is positioned on the downstream of a resistant gene of a carrier. Secondly, the integrated segment is electrically transformed in Escherichia coli expressing recombinase and containing the plasmid with a cloned target gene, and the target site with site-directed mutagenesis and recombinant clone with the resista