With the example of selective catalytic reduction (SCR) denitration technique adopted by domestic thermal power plants, the cost of denitration devices is analyzed in this paper. The top three components of the whole cost are reducing agent, catalyzer, and the depreciation of permanent assets. Based on the cost mentioned above, the denitration electrovalency of coal-fired power plants is estimated. The methods for reducing the cost and enhancing the efficiency of denitration are proposed. The safe precautions for denitration devices are also presented.