The participation of H2O2 in oxidation of the galena mineral and as a result in decreasing of the concentrate recovery of galena mineral has not yet been shown. In this study the effect of two types of grinding media in wet and dry grinding on the formation of hydrogen peroxide and galena flotation was investigated. Laboratory stainless steel ball mill (Model 2VS, CAPCO Test Equipment, Suffolk, UK) was used for grinding galena with mild steel and stainless steel media. Galena ground with mild steel generated more hydrogen peroxide than galena ground with stainless steel media. Galena ground with mild steel has a lower galena recovery than galena ground with stainless steel media. Solutions of 2, 9-dimethyl-1, 10-phenanthroline (DMP) were used for estimating H2O2 amount in pulp liquid with DU® Series 700 UV/Vis Scanning Spectrophotometer. This study highlights the necessity of relooking into galvanic interaction mechanisms between the grinding medium and galena in terms of its flotation behavior.