Abstract: In order to effectively solve the difficult problem of shallow overburden hard and extra thick coal seam in Shendong mining area,taking the 1-2 coal seam of Shendong Huojitu as the research object,the upper layer fully mech- anized mining under layer fully mechanized top coal caving mining technology is adopted for the test. Through numeri- cal simulation,similar material simulation,theoretical analysis and other comprehensive research methods,the influ- ence law of upper layer fully mechanized mining on the under layer top coal cascading is analyzed. The paper puts for- ward the mechanism that,mining large put small,high-impedance bracket up and down disturbance is favorable for re- covery of top coal in under layer fully mechanized top coal caving mining face. Through the application and observation in the mine,the results show that,top coal caving was effectively improved,the top coal behind the stent was full bro- ken,face resource recovery rate achieved 87% ,and the pressure appeared to ease in the under layer fully mechanized top coal caving mining face.