Abstract: By analyzing the impact of the pre-split cutting of key stratum to big structure of laneway surrounding rock and the structure of stope roof，the pre-split can change the fixation boundary of stope roof surrounding rock into the hinged joints boundary.This shortens the transform process of the boundary of the roof board.The pre-split breaks the roof board continuity，and lowers the supporting stress of stope laneway side.Short cantilever beam transfers the part of load from upper strata into the depth to reduce the plastic yield scope of surrounding rock in stope laneway.Therefore the pre-split cutting of stope roof can weaken the boundary restriction of stope roof and control the fracture function of surrounding rock.

Key words: Stope roof structure, Pre-interstitial, Bboundary condition, Supporting pressure