a dna polymerase , having an amino acid sequence represented by seq id no . 2 , or a derivative of the amino acid sequence by substitution , deletion , or addition of at least one amino acid residue . the dna polymerase is a hybrid dna polymerase prepared by inserting a thioredoxin binding domain of bacteriophage t7 dna polymerase into a dna polymerase i of staphylococcus aureus . a method for preparing the dna polymerase includes : 1 ) determining a corresponding position and a target substitution sequence in sau protein for the tbd of the bacteriophage t7 dna polymerase ; 2 ) devising and synthesizing a primer according to a gene sequence of sau and a sequence tbd published by genbank ; 3 ) cloning the sau - tbd segment acquired in to an expression vector ptrc99a to construct a recombinant vector ptrc99a - sau - tbd ; and 4 ) transforming escherichia coli by the recombinant vector ptrc99a - sau - tbd and inducing protein expression .