SO₂ in coal-fired boiler flue gas is one of the main sources of air pollution in our country. Reducing SO₂ emissions and controlling air pollution are  important subjects of environmental protection. Magnesium oxide wet flue gas desulfurization technology is a kind of economical and practical desulfurization method, it has the characteristics of high desulfurization efficiency, low investment cost, small occupation area, low running cost, no secondary pollution etc.. A enterprise 260 t/h circulating fluidized bed boiler flue gas was treated by using magnesium oxide wet flue gas desulfurization technology, the desulfurization efficiency could reach more than 95%, the concentration of SO₂ in flue gas was lower than 50 mg/m³ after the treatment, the desulfurization effect could reach the current environmental protection emission standard.