PCR polymerase technology mainly includes: ① high-temperature denaturation: promoting the dissociation of the extracted original DNA double stranded (template) and the amplified double stranded DNA at a temperature of 94 ℃, forming a single strand, preparing for subsequent amplification; ② Low temperature annealing renaturation: At 55 ℃, the unraveled DNA single strand binds to upstream and downstream primers; ③ Thermophilic extension: DNA template primer conjugate, under the action of Taq DNA polymerase, takes dNTP as raw material and continues to extend along the primer to generate a replication chain paired with template DNA. These three steps go round and round, and the new DNA strand generated in the previous cycle becomes the template for the next cycle, which can amplify the target gene by hundreds of thousands or even millions of times in a short period of time.