Abstract: In order to reveal the mechanism of rib spalling of working face with large mining height and determine the position and the depth of rib spalling. Based on elastic mechanics, PFC^2D numerical simulation and other methods, this paper studies the mechanism of rib spalling of 12511 fully mechanized working face with large mining height in Bulianta Coal Mine of Shendong Mining Area, reveals the characteristics of gradual deterioration of coal wall in working face, establishes the mechanical model of the “thin plate” and calculating formula of rib spalling depth, and then deduces the deflection equation of coal wall deformation to determine the technology of support protection structure controlling rib spalling. The results indicate that instability point is located at 0.579 times of the mining height, the maximum depth of rib spalling is 0.98 m to 1.61 m; adjusting the front-end structure of the roof beam of the working face, the average support strength of the support coal wall protection structure of working face supports should be greater than 0.16 MPa.