The kit is suitable for the extraction of 1-5 ml bacterial cells. Based on the traditional alkaline lysis method, the kit uses a unique silica matrix membrane adsorption technology and reagent formulation. Each column can adsorb up to 30 ug of plasmid DNA, through the effective and specific binding of plasmid DNA under high salt condition. Proteins, genomes, RNA and other impurities can be maximumly removed. The plasmid DNA extracted can be directly used for biological experiments such as cell transfection, PCR, enzyme digestion, sequencing, and ligation.