According to the problem of hard dirt band pre-splitting in the coal seam of the working face, combined with the large range of hard dirt band strata locally occurring in the 112201 ultra-long fully mechanized mining face of xiaobaotang coal mine,breakthrough the limitation of single coal seam pre-splitting technology, proposed a new technique of pre-splitting hard dirt band in coal seam under the combined action of “gas - liquid – acid”, including high pressure water jet cutting technology, carbon dioxide pre-splitting and acid softening technology. By studying the principle and technology of gas-liquid-acid comprehensive pre-splitting technology, the high pressure water jet slotting technology, carbon dioxide pre-splitting and acid softening technology were determined, a gas-liquid-acid pre-splitting test scheme for local and large range of hard dirt band in 350m long working face is designed.field test results show: after the implementation of the scheme, the cutting efficiency and daily production capacity of the shearer were significantly improved, and the consumption of cutting teeth was greatly reduced, the capacity reached 40,000 tons per day, a 35% increase from before the scheme, consumption of coal teeth per ton fell to 40 with a 50% drop, oil consumption per ton of coal decreased by 29.4%. The crushing process is composed of high pressure water jet slot-gas blasting and acid-liquid softening according to a certain process, which has a directional effect, good controllability of crushing network, and no disturbance to the roof and floor of coal seam of working face, ensuring the safety and cutting efficiency of fully mechanized mining face. It provides a new technical method for the hard dirt band pre-splitting in the coal seam of the working face.