Arsenic is a very poisonous element for human health. Unfortunately, due to proximity with industrial centers, some cities are highly poisoned with arsenic. Nowadays production of engineering bacteria which can absorb arsenic effectively has caught scientist’s attention. In general, phytochelatins are known as one group of protein chelators in plants with high binding affinity to heavy metals. Phytoclatins are a family of cysteine-rich peptides and their general formula is (y-Glu-Cys) n -Gly that “n” can be from 2 to 11. Phytochelatins are produced in a metabolic pathway from the precursor glutathione by an enzyme called phytochelatin synthase (PCS). The activity of the enzyme phytoclatin synthase is strongly regulated by metal ions such as cadmium, arsenic, lead and mercury. In the present work, RNA was extracted from the leaves of Helianthius annuus and cDNA was prepared by reverse transcription. Using the specific primers which was designed based on the PCS sequence the gene encoding PCS was amplified and cloned in the expression vectors pET28a and pET41a. The new constructs were transformed to strains Rosetta (DE3). The protein His-PCS was expressed in R-28-PCS after induction with IPTG in the strain R-pET-PCS. However the dominant amount of protein was remained in the form of inclusion bodies. The transfer of protein from insoluble form to soluble fraction was enhanced when the protein was heterologously expressed as GST-PCS using pET41a as vector. However, still the high amount of protein was in the unsalable fraction. To cope with this problem the construct pET41a-PCS was transferred to Rosetta gami2. In this strain the solubility of GST-PCS was enhanced to 70%. In order to study the synthesis of phytochelatin, the HPLC analysis using PC3 as a commercial standard was performd. Phytochelatin production was confirmed in presence of AS 3+ , As 5+ and Cd 2+ ions by HPLC. Nevertheless, when Rg-41-PCS was grown in medium lacking metals, no phytochelatin production was observed. This finding shows that phytochelatin synthase is active only in presence of metals, and its activity leads to phytochelatin production. Rg-41-PCS strain growth curve in medium containing As 5+ ion and its comparison with control strain growth curve in similar medium shows resistance of this strain to As 5+ ion. Also, this strain was able to absorb 10.67 µlmol/gDCW As 5+ in the medium containing 0.5 mM As 5+ . Although according to growth curve of Rg-41-PCS strain, no resistance to As 3+ and Cd 2+ was observed, but this strain was able to absorb 7.58 µmol/gDCW As 3+ and 25.97 µmol/gDCW in medium containing 0.5 mm As 3+ and Cd 2+ . The accumulated amounts of ions in these engineered strains have been high. Therefore, PCS gene can be introduced as a suitable gene for genetic engineering of soil bacteria. Key terms: Sunflower, Phytochelatin synthase, Phytochelatin, Arsenic, Cadmium, Recombinant protein, Transgenic strains, Accumulation of metal