This paper investigates the friction characteristics of drill pipes during directional long-hole drilling in coal mines, addressing engineering challenges such as high friction resistance, low advancement efficiency, and susceptibility to drill pipe jamming. Based on the contact mechanics between the drill pipe system and borehole wall, an axial friction resistance model for drill pipes was established. This model comprehensively considers factors such as borehole depth, rock formation combinations, friction coefficients, and borehole inclination angle. Through multi-condition numerical simulation, the variation patterns of friction resistance under different formation combinations and drilling parameters were analysed. Findings indicate that axial drill pipe friction exhibits non-linear cumulative behaviour with increasing borehole depth. Each 100-metre increase in depth adds approximately 10–12 kN of friction, with maximum differential values of around 7 kN across varying stratigraphic combinations. Furthermore, the borehole inclination angle and rig thrust exert a more pronounced influence on the friction accumulation rate, whereas the drill pipe rotational speed and torque parameters have a relatively weaker effect on cumulative friction. These findings provide quantitative evidence and engineering references for friction control, drilling parameter optimisation, and construction risk prediction during directional long-hole drilling operations in coal mines.