Abstract: With the research technique of the compressive stress experiment in laboratory,theoretical analysis and the field measurement,taking the actual production of large mining height working face in Hedong coal mine as background,the spalling mechanism in working face of large mining height tonstein coal seam has been studied.The research indicated that the single axle compressive strength of non-coupling superposition specimens is larger than the pure coal sample intensity without tonstein,and the deformation amount is smaller than pure coal sample.The theory analysis of the coal wall spalling model indicated that the main influencing factors for the coal wall stability is the coal seam whole height,under the same external force condition,more higher of the coal seam height is,more easier of the coal wall instability is,the tonstein layers reduce the overall thickness of coal seam effectively,the spalling degree of the working face is obviously small.The rib spalling phenomenon of the tonstein coal seam mainly occured in the upside position of the 10^# coal seam in Hedong coal mine,the rib spalling area is not big,and the influence degree is also small.