Abstract: The study objective in this paper is the coal briquette in different particle size from the K₁ coal seam of Chongqing Datong 1^# Mine,by utilizing the self-developed triaxial servo-controlled seepage equipment for thermo-fluid-solid coupling of coal containing machine, we propose a new computing method of volumetric strain in accordance of deformed shape in process of test to find the relationship between the seepage characteristic and volumetric strain in the condition of coal briquette in difference particle size. Test results show that seepage velocity is related to the particle size; seepage velocity in large particle size of coal briquette is faster than it in small particle size when the coal briquette test specimen is uniformity; the higher of particle size which is from 180 to 250 μm, the slower of the seepage velocity. There is a better relation between seepage velocity and volumetric strain. Seepage velocity is linear reduction in every particle size in the stage of volumetric strain decreasing. The seepage velocity will maintain steady when the content of 180 to 250 μm mesh corn is upon a level in the stage of volume increase reversing. In contrast, when the content of 180 to 250 μm mesh corn is under a level, the seepage velocity will increase. The increased velocity of seepage velocity is slower than the reduced velocity.