Abstract: To solve the problem of low gas extraction rate caused by the low permeability of coal seams in deep mining, based on the theoretical basis of hydraulic fracturing and acid enhanced permeability, an acid fracturing composite permeability-enhancing technology is proposed for interlayer drilling by iterating fracturing fluid as acid fluid.Field experiments are conducted for comparative analysis.By comparing the changes in gas mixture flow rate, extraction concentration, and purity before and after acid fracturing drilling and ordinary drilling, the gas extraction effect after acid fracturing is compared.Research has shown that after acid fracturing, the average single hole mixed flow rate of the acid drilling group increased by 2.1 to 3.5 times compared to the ordinary drilling group; The average single hole concentration has increased by nearly 50% compared to the ordinary through-layer drilling group.The average single hole gas extraction purity has increased by 3.9 to 5.8 times, and the gas extraction effect of boreholes after acid fracturing is significantly better than that of ordinary through-layer boreholes.