Abstract: The difficulty of roof maintenance is a key problem that restricts the safe and efficient production and equipment withdrawal of fully mechanized mining face.The deformation and breakage mechanism of composite roof and the diffusion law of grouting slurry are studied by theoretical analysis, numerical simulation and field measurement in the 112203 working face of Xiaobaodang Coal Mine.The results show that the roof failure of the working face is divided into recompaction zone, end caving zone, fracture through zone, disturbed zone and undisturbed zone, and the fracture caving of composite roof is influenced by the instability of the coal wall.Grout diffusion radius is positively correlated with the permeability coefficient of coal and rock mass and the grouting pressure.Reasonable grouting pressure can achieve the best economic and technical effect for grouting reinforcement.The grouting reinforcement scheme of the 112203 working face retreating roadway's crushing composite roof is put forward, and the roof breakage and subsidence are effectively controlled.