Abstract: In order to improve the problem of insufficient caving and low resource recovery rate of hard top coal in steeply inclined and extra-thick coal seam in the northern mining area of Wudong Coal Mine in Xinjiang，the pre-splitting technology of water injection-blasting coupling fracturing top coal is studied. According to the coal seam occurrence and working face space conditions，the theoretical calcula⁃ tion，parameter design，field test and multi-source monitoring are combined to determine the water injec⁃ tion pressure，water injection volume，hole sealing length，hole angle and charge parameters，and form the fan-shaped grouping staggered hole arrangement and the forward continuous charge scheme in the hole. By using KJ21 mining pressure monitoring system，bolt force sensor，borehole stress sensor and transient electromagnetic detection，the top coal stress，electrical characteristics and caving effect before and after the implementation of the measures are compared and evaluated. The results show that when the water in⁃ jection pressure is 10 MPa and the water injection amount of single hole is 39.09 t，the effect of coal infil⁃ tration and softening is better .After using 113 mm diameter blastholes，4 m hole spacing and 2 m staggered spacing，a continuous overlapping damage zone can be formed in the depth range of 20 m of top coal. After the coupling pre-splitting，the average stress of the bolt decreases from 11.5 kN to 6.6 kN，with a decrease of 42.6%. The average surrounding rock stress of the borehole decreased from 5.73 MPa to 4.89 MPa，with a decrease of 14.7%. The minimum apparent resistivity of the pre-splitting zone is 5~15 Ω · m，which is 62.5%~7.5% lower than that of the non-blasting zone. The low-resistance anomaly range has a good corre⁃spondence with the borehole action zone. The research shows that water injection softening and blasting fracturing can synergistically promote the stress release and fracture penetration of top coal，which pro⁃ vides technical support for efficient pre-splitting and safe mining of hard top coal in similar steeply in⁃ clined and extra-thick coal seams.

Key words: steeply inclined and extra-thick coal seam, pre-splitting of top coal, fully mechanized caving mining, water injection-blasting coupling fracturing