In order to prevent water burst in No. 15 coal seam mining of Longwan Coalfield, the coal seam floor water-resisting layer and spatial distribution were analyzed, the distance between coal seam floor and bottom Ordovician is 40.92～2.70 m, waterhead pressure of No. 15 coal seam floor is 0～7.11 MPa, grouting reconstruction process was adopted, under Ordovician top 50 m relative water-resisting layer condition, the coal seam water burst coefficient is 0.01～0.123 MPa/m, average 0.050 MPa/m, more than 90% of the area is in no pressure area and relatively safe mining with pressure.