Abstarct: Periclase powders with MgO formula, is one of the useble refractories in superallays industry which is obtained from magnesia and magnesia choloride. The presence of SiO2 and CaO impurities because of fusible minerals formation, has the most effect on the ability of periclase for being refractory. In order to have the ability of getting used in refractoey industry, the CaO to SiO2 ratio in magnesia should be higher than two or lower than 0.38. The purpose of this thesis, is investigating the possibility of reducing the impurities of magnesia in Torshak Mohammadi region. Torshak Mohammadi birjand magnesia includes 89% of MgO and the CaO/SiO2 ratio is about one. Analysing the inverse flotation experiments showed that for obtaining the maximum MgO grade, parameters such as depressant and solid percentage have the most effect on the MgO grade. The interaction between pH, depressant, collector and collector assistant are also significant. Finally, using Winrobust software estimated that the most MgO grade is about 92.04%. According to the experiments analysis, the CaO to SiO2 ratio, cannot be increased to more than two and also less than o.38. The results showed that depressant, collector assistance and frother have the most effect on CaO to SiO2 ratio and also pH, depressant, collector and collector assistance factors had significant interactions on CaO/SiO2 ratio. finally using Winrobust software, it was estimated that the minimum ratio of CaO/SiO2 is 0.56 which is not useful for using magnesia production in refractory.