Abstract: Accurate determination of in-situ gas pressure in deep coal seams is crucial to the safe production of coal mines. However, the traditional coring and pressure measurement techniques do not take into account the complexity of the gas composition in the coal seam and ignore the effect of the expansion of the free volume of the coal samples on the in-situ gas pressure during the coring process, which reduces the accuracy of the in-situ gas pressure measurement. Based on the concept of pressure-preserving gas coring in deep coal seams and focusing on the gas pressure rebalancing process caused by the expansion of the free volume of coal samples after coring, we independently developed a multi-gas component desorption system for in-situ pressure-preserving coal samples, and systematically carried out pressure-preserving coal sample desorption experiments under a multi-gas component environment, which reveals the mechanism of the influence of different gas components on the dynamic evolution of the in-situ gas pressure. The results show that: ① the gas pressure change during the whole process of fidelity coring can be divided into the initial adsorption equilibrium stage, the variable volume stage and the desorption equilibrium stage, while the variable volume stage is the main stage of the gas pressure change, and the rate of pressure decay decreases gradually with the expansion of the volume; ② the change of the gas pressure is affected by the degree of expansion of the coring volume, the initial adsorption amount and the gas competition for adsorption, and the expansion of the free volume will result in the The free volume expansion will lead to an increase in the mean free range of gas molecules, which will weaken the frequency and intensity of intermolecular collisions and contribute to the decrease of gas pressure; ③ The presence of strongly adsorbable gases (e.g., CO₂) has a buffering effect on the decay of gas pressure in the pressure-retaining coal samples, whereas the weakly adsorbable gases (e.g., N₂) accelerated the decrease of gas pressure; ④ In the process of the pressure-retaining coal samples coring, the competitive adsorption characteristics of CO₂ significantly modulate the change of gas pressure, and CH₄ dominated the initial gas pressure change, with CH₄ dominating the initial gas pressure. change, CH₄ dominates the initial gas pressure change, and N₂ desorption increases in the low-pressure stage. The results of this study can provide a new method for accurately obtaining the gas pressure in deep coal seams by pressure preservation coring, and provide technical support for judging the gas extraction standard and checking the effect of anti-surge measures in coal mines.