After coal mined, the balance of original stress state is to be broken. In the course of retribution, displacement and deformation in the overburden takes place with the working face advancing. The article points out that overburden can be divided into, in ascending, caving zone, fractured zone, bending zone and loose alluvium zone. The extracting space can be prevented from transferring to ground with injection material into bed-separation gap. Applying both mining subsidence theory and elastic thin plate theory, the computational model of subsidence control technology of grouting is worked out. The model can get rid of blindness of determining the position of separated strata, forecast the surface subsidence and provide the basis of theory for forecasting surface subsidence control technology of grouting.