In the flotation of sulfide minerals, particularly in the separation between pyrite and chalcopyrite, adjustment of the pH and reagents dosages is very important. Process auditing at the Sarcheshmeh copper complex showed that the pH in the rougher cells was greater than 12, while according to the initial design, the pH in the rougher cells should be 11. 5. Also, it was found that the collectors and frothers dosages were 21. 6 and 25. 1 g/t, respectively, which is much lower than the initial design. Also, plant audit showed that this operation method was used because of an idea about higher froth stability and easier operation in the higher pH values. In addition, it was observed that by suddenly changing the reagents and pH regime to the initial design, operation stability and therefore the copper recovery were also reduced quickly. Hence, in this study pH was decreased and reagent dosages were increased step by step. The results showed that after adjustment of the pH in the range of 11. 5-11. 7 and increasing the collectors and frothers dosages to 29 and 31 g/t, respectively, the copper recovery was increased by about 2%, and the operation stability was not reduced.