<p>To calculate the hydrogeological parameters of the Cambrian thick limestone aquifer beneath the coal seam floor in the newly developed Xiadian coalfield, North China, a multi-borehole, high-discharge, long-duration water release test was conducted in underground tunnels at depths exceeding 800 m. This test overcame the limitations of conventional pumping, water pressure, and tracer tests, which are constrained by discharge capacity, test scale, and applicability, and enabled long-term observation of hydraulic responses in a deep confined aquifer. During the test, the maximum total water release rate reached 393.14 m³/h, with a duration of 508.17 h. The maximum groundwater drawdown in the Cambrian limestone aquifer was 127.46 m. Using the unsteady-state Jacob formula, a superposition model was developed to relate drawdown to flow rate. This model allowed the calculation of the aquifer’s transmissivity coefficient, storage coefficient, discharge per unit drawdown, and specific capacity. As the result shows: (1) The multi-borehole, long-duration water release test effectively stimulates the aquifer’s groundwater flow field, overcoming the limitations of surface small-flow tests. (2) The drawdown-flow relationship model accounts for the hydraulic interference among multiple release points, and the derived hydrogeological parameters align with field observations. These findings provide a reliable technical basis for parameter acquisition and inversion in deep (&gt;800 m) high-pressure confined aquifers, and for developing drainage and depressurization strategies in similar deep coal mines.</p>