Abstract: in order to provide theoretical support to the through stata fracturing technology of horizontal l in the roof and foo of sean.taking through strata fracturing technology of horizontal ell in the roof and foo of seam as th simulation objct a large size rue triaxil test systemn was aplied tothe racturing simulation test of horizontal ell n the sample prepared with the naural rock samples,and a study was conducted on the in titu sress,natural crack and elastic modulus affected tothe expansion of the hydraulic cracking. The resuts shcwed that when the through stat fracturing technocgy of the horizontal vell as aplied todeveloag the coaltedmethane ,a coal beaing stratum with a max high stress difference betwee the verical stress and horzonal tress( 5 MPaj should be optimally seleced.n the high elastic moduus stratum,the pressure in the lhydraulic fractured cracks would be high and the cracks could be frther expanded.The natural racks wouldinfuence the hyraulic cracking expansion,which would not only related to the approximate ang e but would be related to the with ofthe naturl crack and the iniecion pressure in the ydrauli fractured cracks.The injction pressure in the hydraulic cracks would be low(10 MPa.When the with of the natural crack was wide( 0.05 m),.the hydraulic cracking would be eily afced by the natural cracking and would be expanded along the natural cracking when the natura cracking interaced. 晶hen the injecionpressure in the hydraulic cracks was high( 30 MPa)the natural cracks would reduce the infuences to the expansion of the hydraulic cracks.