Introduction: Mutations are the most popular way to increase the efficiency of mineral waste bioleaching. Acidithiobacillus ferrooxidans are used as an important microorganism in biohydrometallurgy. Arsenate is one of the toxic elements in mines, which reduces the efficiency of A. ferrooxidans leaching. The purpose of this research was to increase the resistance of A. ferrooxidans to high concentrations of arsenate.Materials and Methods: This research was an analytical – descriptive study. The studied population was isolated A. ferrooxidans bacterium from the Sarcheshmeh copper mine in Kerman. The highest tolerable concentration of arsenate was determined by successive cultures of this bacterium at increasing concentrations of arsenate. The bacteria were exposed to UV radiation at different times and then cultured in higher concentrations of arsenate. Results: The results showed that the wild strain was able to grow in the medium containing 20 mM of arsenate. With adaptation, this bacterial strain could grow in medium containing increasing concentrations (40, 60, 80, 100, 120, and 140mM) of arsenate. When the bacterium was exposed to UV ray for 60 minutes, it was able to grow at a concentration of 120 mM of arsenate.Conclusion: The results indicated a very good effect of UV ray on increasing the arsenate resistance of A. ferrooxidans. It is suggested that this modified strain can be used in real environments for bioleaching.