Leaching process of Jiroft refractory manganese ore was investigated. The effects of operating parameters such as liquid to solid ratio, pulp temperature, sulfuric acid concentration, and oxalic acid concentration were studied and the optimization was done through the response surface methodology (RSM) based on central composite design (CCD) model. The recoveries of Mn, Fe and Si were selected as response of design. The optimum condition was determined by ANOVA, indicating that the liquid to solid ratio, oxalic acid concentration and pulp temperature for Mn recovery and liquid to solid ratio, pulp temperature and sulfuric acid concentration for Fe recovery and liquid to solid ratio for Si recovery were the most effective parameters, respectively. Under the optimum conditions of liquid to solid ratio= 11.8%, pulp temperature= 70oC, sulfuric acid concentration= 40 g/L and oxalic acid concentration= 35 g/L, 71.1%, 4.67% and 0.6% of Mn, Fe and Si were recovered, respectively.