GDP-HiFi is a new recombinant enzyme with genetic modification for its amino acid sequence, which results 70 times better fidelity than Taq DNA polymerase and an extremely fast elongation rate (as fast as 15 seconds per kilo base, kb). GDP-HiFi has higher stability at high temperature, and this property makes GDP-HiFi perform very well for GC-rich PCR. Being highly thermo-stable, GDP-HiFi DNA Polymerase can remain viable even after being subjected to boiling for 2 minutes. This special enzyme has been modified genetically and needs less concentration of magnesium than other polymerases. The suggestion for magnesium ion in the reaction is 0.8 to 1.2 mM. 10X GDP-HiFi PCR buffer contains no magnesium. A tube of 25 mM MgSO4 is provided. Further optimization can be achieved for different targets of DNAs. Reagents are provided for 100 PCR reactions of 50 μl each.