Taq DNA polymerase with a relative molecular mass of 94 has a higher activity, about 200,000 U/mg, and has a higher optimum temperature of 75 to 80 °C when synthesizing DNA. Although Taq DNA polymerase has limited ability to synthesize DNA above 90°C, it is still relatively stable at high temperature. Experiments have shown that at 92.5°C, 95°C and 97.5°C, the Taq DNA polymerase in the PCR mixture can still maintain about 50% of the activity after 130 min, 40 min and 5-6 min respectively, and its half-life longer.

Therefore, in a PCR preparatory experiment, the upper limit temperature of each cycle is 95°C for 20S, and the Taq DNA polymerase can still maintain 65% of the activity after 50 cycles, which can meet the needs of the experiment.

Taq DNA polymerase has high processing and synthesis characteristics. When the reaction temperature is suitable, the rate of dNTP incorporation is 35-100 nt/(s. enzyme molecule), and the amplification length can reach 7.6 kb. Under low temperature conditions, the activity of Taq DNA polymerase is significantly reduced, resulting in a hindered ability of the enzyme to extend in local secondary structure regions within the template or a change in the ratio of the forward rate constant to the dissociation constant. At higher temperatures (above 95°C), there is little DNA synthesis; in vitro, the rate of DNA synthesis at higher temperatures is limited by the stability of the primer or the duplex structure of the primer strand and the template strand.

Since the optimum reaction temperature of Taq DNA polymerase is as high as 75-80°C, the annealing temperature and extension temperature can be appropriately increased, which limits the appearance of non-specific amplification products and increases the specificity of PCR reaction.