Abstract: There exists one thick igneous rock between the coal seam and the surface in the coalmine,Shandong province.The igneous rock probably induce great dynamical disasters,thus affect production and threaten miner's safety.Based on the exploration and data collection,the paper analysed failure mechanism of thick igneous rock;obtained failure law of thick igneous rock according to semblable experiment of the rock and provided the theoretical basis in controlling thick igneous rock's broken during the exploitation of coalmine when such similarity structures existing,it was also the foundation in the research of the sink rules of the earth's surface,dynamical disaster analysis、prevention and cure,have some economic benefit and social benefit.