Chromium is a toxic metal with oxidation numbers ranging from –2 to +6. Nonetheless Cr (VI) and Cr (III) are two commonly existing stable oxidation states of chromium in the environment. The Cr (VI)-made-compounds are generally more soluble, mobile, and bioavailable in the environment in comparison with Cr (III)-made-compounds. Besides, chromium (VI) is a notorious inhaled carcinogen and leads to severe health problems ranging from simple skin irritation to lung carcinoma. The elimination of chromium from the environment can be achieved by dint of various chemical and physical approaches. However, the high-energy demands, incomplete elimination, production of toxic sludge are some of disadvantages of these technologies. In recent years, bioremediation has become one of the alternative methods which are of broad appeal through people owing to its high efficiency, low cost and its ecofriendly nature. Hence, the transformation of Cr (VI) to the non-toxic Cr (III) using chromium resistant bacteria offers an affordable and cost-effective option concerning chromate detoxification. In the present work, a gene encoding a chromate reductase named YieF, was overexpressed in E.coli . To this end the gene encoding YieF was amplified from the genome of E. coli by PCR. Then the PCR product was cloned in the expression vector pCDFduet under the promoter T7. The construct pCDFduet-YieF was transformed in E. coli strain Rosetta (DE3) resulted in production of a new strain named R-YieF. The heterologous expression of YieF as a His.tag fusion protein was confirmed in the soluble fraction of E. coli by SDS-PAGE. The comparison of growth curve and determination of the amount of eliminated Cr 6+ in the medium of R-YieF and the control strain showed that the over-expression of YieF has a significant effect on the accumulation of Cr 6+ . In addition we co-expressed YieF with a rice metallothionein isoform (OsMT1) in E. coli . Therefore the construct PCDFduet-YieF together with the previous- made construct pET41a-OsMT1 were transformed in E. coli strain Rosetta (DE3). The new strain was named R- YieF-MT1. The heterologous expression of both His-YieF and GST-OsMT1 were confirmed in the soluble fraction of this strain. Finally the growth curve of the strains R-MT1, R-YieF, R-YieF-MT1 and control strain was compared when the strains were grow up in the medium in the presence of 2 mM Cr 6+ . The results show that the OD after 12 h in the all three transgenic strain was more than control strain. The accumulation of Cr6 + in the new strains as well as control was determined during 0, 2, 6 and 10 h after addition of IPTG and Cr 6+ to the medium. The results showed that the accumulation of Cr 6+ increase in the strains during time. However the amount of accumulation between strains are different and is in order of R-MT1-YieF R-YieF R-MT1 Control which indicate the significant effect of co-expression of MT1 and YieF in the elimination of Cr 6+ . The absorption isotherm showed amount of accumulation of Cr 6+ in the strain R-MT1-Yied is dependent on the primary concentration of Cr 6+ . However the absorption was remained constant when the primary concentration was reached to 3 mM. Keywords : heavy metals, chromium, metallothionein, chromate reductase, protein expression