The thermostable properties of the Taq DNA Polymerase from Thermus aquaticus have contributed greatly to yield, specificity, automation and utility in the PCR for amplification of DNA. Isolation of this protein from T. aquaticus is difficult. Several studies have shown the recombinant expression of Taq DNA Polymerase in heterologous host cells. However, these still suffer from low yields. The use of T7 RNA Polymerase regulated expression vector and availability of affinity tag (His Tag) can make the expression of Taq DNA Polymerase an efficient and economical process. The project is aimed in recombinant expression of Taq DNA Polymerase in BL21 host cell line and pET expression vector.