<p>The gas–liquid combined permeability enhancement technology, which integrates liquid CO₂ phase transition blasting with hydraulic fracturing, can effectively manage the initiation position of hydraulic fractures in coal seams and enhance the migration capacity of CO₂ gas within coal matrices under high-pressure liquid influence. To investigate the impact of high-pressure water injection on CO₂ gas generated by liquid CO₂ phase transition blasting during gas–liquid combined fracturing, a multifunctional fracturing tube capable of gas–liquid combined fracturing was developed. Subsequently, single liquid CO₂ phase transition fracturing and gas–liquid combined fracturing tests were conducted on a large-scale dense artificial sample. The experimental findings indicate that high-pressure liquid injection can significantly extend the migration distance of CO₂ gas within the coal body. Specifically, the migration distance of CO₂ gas on the same horizontal plane inside the briquette during the gas–liquid combined fracturing experiment was at least 25.00% greater than that in the single liquid CO₂ phase transition fracturing experiment. High-pressure liquid can facilitate greater CO₂ gas adsorption in coal, with the amount of CO₂ gas released in the single liquid CO₂ phase transition fracturing experiment being 24.60 times that of the gas–liquid combined fracturing experiment. Moreover, the relationship between the migration distance and time of high-pressure CO₂ gas generated by liquid CO₂ phase transition blasting on the same horizontal plane within the briquette adheres to an exponential function. These research findings hold significant implications for understanding the mechanism of permeability enhancement and promoting drainage through gas–liquid combined permeability enhancement technology, ultimately contributing to improved coalbed methane mining efficiency.</p>