Abstract:Bacterial genomic DNA extraction quality directly affect the rapid test results based on PCR，including the detection speed，sensitivity，detection limit and other indicators. The concentration of cell culture is very important，too thick or too low concentrations will bring interference to the subsequent operation of PCR. In order to get the concentration of cell culture simply and conveniently，the Maxwell nephelometer were used to determine the cell concentration in the supernatant，at the same time validated the data using the plate count method. It showed that Maxwell nephelometer could match the determination purpose and measure the concentration of bacteria quickly and accurately. The standard curve of bacteria concentration were made， compared with the genome content，they have relevance. Different methods of extracting genome were compared to determine the extraction efficiency，at last the third：modified Universal Genomic DNA Extraction Lit Ver.3.0 method was selected.