Abstract:With the help of the research methods of similarity model test s , the problems about top coal caving of specially thick coal seam of coal No. 5 of Baicaoyu well field in Huating mine administ ration is discussed. Three similar material model test s show that the top coal caving mining with three layers is reasonable , but the top coal caving mining with two layers is not reasonable. The coal2recycling ratio with three layers can meet engineering re2 quirement , but the coal2recycling ratio with two layers is very low. The optimal layer2divided thickness is 12~15 m and the optimal ratio of mining to caving is 1∶3.