The invention belongs to the technical field of the resource treatment of industrial wastes, and particularly relates to a method for preparing a cementing material using smelting industrial waste slag after utilizing the simultaneous removal of SO2 and NOx in flue gas and an application of the cementing material obtained by the same. According to the invention, SO2 and NOx in the flue gas can be treated with the smelting industrial waste slag, meeting requirement of flue gas desulfurization and denitration; moreover, the smelting industrial waste slag can be purified and separated by means of waste gas resources to obtain a cementing material, realizing the resource utilization of the smelting industrial waste slag and waste gas.