The invention discloses a gene fragment which has a nucleotide sequence as shown in SEQ ID NO.1; the invention also provides a vector pPlasmid-Clearance, wherein the vector pPlasmid-Clearance is constructed by inserting the gene fragment having the nucleotide sequence as shown in SEQ ID NO.1 into a resistance gene region of a conjugal transfer vector pEF01 through a homologous recombination method; the conjugal transfer vector pEF01 has the nucleotide sequence as shown in SEQ ID NO.2. The gene fragment and the vector pPlasmid-Clearance can reverse the drug resistance of drug resistant bacteria of polymyxin drug-resistant gene mcr-1 in bacterial flora of environments and animals, can block the spread of polymyxin drug-resistant gene mcr-1, and have great application potential in the prevention and clinical treatment of bacterial diseases.