Abstract: To solve the hidden trouble in roof oblique segmentation section of short wall mining face, through theoretical analysis, numerical simulation and field surrounding rock deformation monitoring and roof pre-splitting blasting, we study steep medium thickness A3 coal seam,and the results show that: the longer the length of the hanging arch, the greater the safety hidden danger of short wall working face; high stress of cavern roof, the large displacement change are mainly concentrated in the range of 70 m to 120 m from the cut-hole, and the results are verified by stress on-line monitoring; for oblique segmentation working face,we propose roof pre-splitting blasting scheme; we propose corresponding roof pre-splitting blasting, and contrast surrounding rock deformation before and after the implementation of roof pre-splitting blasting, and verify the roof blasting effect.