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In view of the dynamic disaster problems involved with the trigone hard and stable roof of head face in Northern Shaanxi Jurassic large mining height coal seam.This paper uses theoretical analysis, numerical simulation and field test to study the large area of roof destruction in the artificial interference, which includes coupling evolution law of hydraulic cracks and stress field in hard roof.The hydraulic fracturing technology is used to cut the top of the roof in order to generate directional fracture and to control the trigone roof breaking evolution direction of fracture.It can achieve directional cutting and breaking of hard roof,so as to effectively control the mining ground pressure.The research shows that the roof is converted from the tensile failure before fracturing damage into the tensile shear failure after fracturing.Fracturing directional crack tip formed wing crack and anti wing crack.Roof breaking angle by 45 degrees before fracturing into 56 degrees fracturing after.The caving step distance is changed to 10 m after the roof fracturing which can effectively control with the dynamic disaster of roof caving.