Abstract: This study systematically investigated the effects of varying concentrations of α-alkyl sulfonate (AOS) additives on the rheological properties of coal-water slurry during pipeline transport, using both a circulating pipeline delivery system and a rotational rheometer. A detailed comparative analysis of data from both testing methods was conducted. The results demonstrated that AOS exhibited a significant viscosity-reducing effect on the slurry in both methods. However, at low concentrations, around 0.02% (mass fraction), the viscosity reduction was minimal, and at certain shear rates, a slight viscosity increase was observed. As the AOS concentration increased to below 0.5% (mass fraction), the slurry viscosity decreased rapidly at various shear rates. When the concentration exceeded 0.5% (mass fraction), the rate of viscosity reduction gradually slowed. At 1.2% (mass fraction) AOS concentration, the viscosity of the slurry became almost constant, with a viscosity reduction rate exceeding 60% across all shear rates. Furthermore, the viscosity-reducing effect of AOS was dependent on shear rate. Below 0.5% (mass fraction), the viscosity reduction initially weakened before strengthening as shear rate increased. Above 0.5% (mass fraction), the effect became more complex, exhibiting two increases and two decreases as shear rate rose. The above experimental data not only confirmed the significant viscosity-reducing effect of AOS on coal-water slurry but also revealed the specific impact of AOS concentration and shear rate on viscosity reduction, providing valuable experimental data for the regulation of slurry rheological properties.