Abstract: In this paper, the mining failure feature and form of the incline and thin coal seam's floor is researched by using the test result of the continuous exploration system with multi pipeline in the borehole and the analyses of fracture mechanics.The result indicates that the floor's failure form likes a spoon.The difference between the failure feature of thin coal seam and the ones of thick coal seam is that the mining fractures in the floor are mainly the expansion of original joints and fractures, and the most fractures tend to close after the working face passed and the floor's rock strata are compacted.