The invention relates to a method for restoring steep slopes of a mining area by mechanical spraying of lime neutralizing sludge slag. The method comprises the following steps and conditions of addingtailing slag into the lime neutralizing sludge slag, mechanically stirring according to a mass ratio of 100:(70 to 300), and uniformly mixing, so as to obtain a mixed material a; adding an organic fertilizer, a composite fertilizer and grass seeds into the mixed material a, mechanically stirring according to a mass ratio of 100:(2 to 6):(0.1 to 0.3), and uniformly mixing, so as to obtain a mixedmaterial b; screening the mixed material b by a vibration screen, grading the coarse and fine materials, enabling the material under the screen to fall into a material bin of a spraying machine, and using as a dry powder mechanical spraying material; enabling a pipeline and pressure air flow to convey the spraying material to perform dry powder mechanical spraying on the area requiring ecologicalrestoration; covering a nonwoven fabric onto the sprayed area, and performing proper servicing management on the area according to the local climate environment. The method has the advantages that theneutralizing sludge slag can be applied to the dry powder mechanical spraying, the 'guest soil' material is protected, the loss of water and soil is prevented, the energy-saving and consumption-decreasing effects are realized, the method is suitable for the rooting, germinating and later fertilizer applying and caring of the plant grass seeds, the ecological environment benefit is good, and the like; the method is suitable for being applied into the field of ecological restoration of the mine areas.