Abstract: Stability of the coal wall problems has been seriously affected the normal operations in fully mechanized caving with great mining height, which results in difficult to achieve high efficiency of mining. Therefore, we studied the mechanism and impact factors of rib spalling through theoretical analysis, numerical simulation and field practice. Then we simplified coal wall stress of working face as a compression strut model, and calculated that the reason why maximum displacement occurring at the middle of whole height of coal wall. Come to the conclusion that reducing mining height, the working surface oblique mining, increasing the working resistance of hydraulic support, accelerating advance rate of working face and coal injection grouting can help control the problem of rib spalling with very thick coal seam.