The invention discloses a gas and cement slurry mixed deep-hole circulation high-pressure splitting grouting method. The segmented circulating construction is performed on grouting holes (drilling holes) of a fully mechanized coal mining face top plate, which means that the grouting holes are divided into n segments according to the length of the grouting holes, firstly, the construction is performed at first segments at orifices, the construction comprises sequential drilling and grouting work, the construction of a second segment is carried out after the construction of the first segment iscompleted, the cycle is completed until the construction of n segments is completed. A geological drilling rig is used to construct the grouting holes in the fully mechanized coal mining face top plate according to set positions, and a condition that the positions of the drilled grouting holes are in fully mechanized coal mining face top plate mudstones or dirt bands is guaranteed. According to the method, the alternating grouting process of single-numbered and double-number grouting holes is employed, certain pressure-relieving zones can be formed around the grouting holes, water or gas in cracks is timely discharged, the resistance of the diffusion of slurry in the cracks is reduced, the fluidity of cement-based slurry is improved, the grouting diffusion radius is enlarged, and the microcrack grouting effect is ensured.