Abstract: Aiming at the field measurement problem of roof mining failure zone after mining, in order to master the height of fractured zone in roof strata caused by underground mining and ensure the safe mining above the water-bearing stratum. In this paper, the method of the empirical formula prediction and FLAC3D numerical simulation was adopted to study the height of the roof mining fractured zone in a coal, and then the system of double ends borehole plugging device in measuring leakage was applied to the measurement to verify the results of the empirical formula prediction and the numerical simulation, and the three results were compared with each other. The research shows that :(1) the theoretical formula estimated value of the height of coal roof mining failure zone is 41.3m , the result of the numerical simulation is 33.92m，and the result of field measurement is 37.67m . The result of the numerical simulation is basically close to that of the field measurement. However, the result of the empirical formula is expected to be conservative. After comprehensive consideration, the roof strata maximum fractured failure height of the working face is 37.67m; (2) With the advancing of the working face, the plastic zone of the roof strata is still increasing. When the working face reaches 90m, the development height of the roof strata fracture reaches the maximum value of 33.92m, and the height is no longer increased. Its shape is a straight line which is approximately parallel to the top of coal seam , and the change trend of the roof plastic zone is consistent with that of the maximum principal stress; (3) from the section of coal seam tendency, the shape of the roof plastic zone is approximate to the saddle shape, which is consistent with the actual situation. In summary, the results of simulation and field measurement of coal roof mining failure zone can guide the coal mine safety production, and provides an important scientific basis for the prevention and control of mine water, and has important practical value.