The results of previous studies in Iran industry sector have revealed the fact that effective monopoly structure is dominant in more than 50% of activitiesinthe sector. The purpose of this study is to evaluate, the amount of social cost of such structure has imposed to society because of dominating effective monopoly structure in Iran industry sector. In this research, the calculations related to estimation the social cost of monopoly have been done in Iran industry in 2011, based on Posner and Harberger's indices. according to Harberger 's approach and first scenery,this index is calculated for monopoly industries, over7% of monopoly industry sale, is the social cost imposed to society.Also this ratio will be more than 26% according to Posner's index; i.e. in addition to welfare triangle, economic rent,and spend cost for monopoly power trade, social cost that monopoly industry imposes to society is about 26.7% of this sale if it is assumed as a sector of social cost.And, if basedon Harberger's approach and second scenery, this index is calculatedfor monopoly industry, more than 5.4% of monopoly industry sale, is the social cost imposed to society. This ratio, also, will be more than 23.9% based on Posner's index.