<p>In coal mine anchor hole drilling, cuttings discharge efficiency directly impacts energy consumption and construction stability. This study, based on the specialized drill structure and positive circulation hydraulic cuttings discharge process, employs CFD-DEM coupling to simulate drilling in limestone, coarse sandstone, and coal seams. It investigates the effects of rotational speed (<i>n</i>), drilling rate (<i>v</i>), and flushing pressure (<i>p</i>) on multiphase flow field characteristics, particle migration behavior, and discharge efficiency, achieving bidirectional dynamic simulation of flushing fluid and cuttings transport. Results reveal a complex circulating flow at the bit outlet, comprising a main jet, backflow, and local stagnation zones. Within the hole, the flow follows an ‘upward in the center, downward at the periphery’ pattern, while cuttings particles ascend spirally but are prone to deposition at the bottom due to reflux. To quantify performance, Cuttings Removal Efficiency (CRE) is introduced, with orthogonal experiments, range analysis, variance analysis, and multiple regression yielding predictive models per rock type. Flushing pressure dominates in hard rocks, while rotational speed is more sensitive in soft coals. Models achieve <i>R²</i> &gt; 0.81 and average error &lt; 10%. This work elucidates multiphase flow and migration mechanisms, providing a predictive framework and parameter optimization for reducing stuck drilling risks and enhancing efficient, stable operations.</p> Graphical abstract <p></p>