Abstract: Aiming at the challenges of high resistance loss and severe pipeline wear in long-distance gravity transport of coal mine backfill slurry, we take a composite backfill slurry of fly ash, desulfurization gypsum, cement, and quicklime as the research object. The pipeline transport resistance characteristics under different pipe diameters (\phi 100 mm, \phi 150 mm), flow velocities (0.8～1.8 m/s), and mass concentrations (50%～60%) were investigated using a loop pipeline test system. The results show that for a given pipe diameter, the slurry resistance loss increases significantly with increasing flow velocity. Under the same flow rate, a larger pipe diameter can effectively reduce resistance loss (e.g., at a flow velocity of 1.41 m/s, the head loss of the \phi 100 mm pipe is 0.49 kPa/m, while that of the \phi 150 mm pipe decreases to 0.32 kPa/m). As the concentration increases, the resistance loss exhibits a trend of first decreasing and then increasing, with a mass concentration of 55% identified as the critical point (the \phi 100 mm pipe achieves minimum resistance at a flow velocity of 1.41 m/s). Analysis indicates that within this concentration range, the increased slurry viscosity suppresses the turbulence intensity of the water flow and weakens the effective gravity of the slurry, leading to an abnormal decrease in the hydraulic gradient. The smaller pipe diameter (\phi 100 mm) results in significantly higher energy consumption than the larger one (\phi 150 mm) due to enhanced slurry–pipe wall interaction. The slurry with 55% mass concentration can minimize resistance, providing a core parameter basis for the long-distance gravity transport system at Zhaoshipan Coal Mine. This study reveals the regulation mechanism of pipeline transport resistance for multi-component solid waste-based slurry and lays an experimental foundation for energy saving, consumption reduction, and optimized engineering design of backfill systems.