Abstract: The coal-based solid waste filling mining technology is a significant representative technology for achieving green and low-carbon coal mining. Filling the goaf with coal-based solid waste slurry can effectively control the movement of roof strata and prevent derived disasters. The research is conducted on the stability of slurry suspending state, in response to the issue of strong sensitivity of particle suspension in long-distance pipeline transportation of coal-based solid waste filling slurry, which can easily lead to unstable slurry concentration then pipeline blockage or bursts, under the developing trend of intelligent and large-scale coal mining. The aim is to reduce pipe blockage and burst accidents of long-distance filling mining of coal-based solid waste. Firstly, by applying orthogonal experiments, range analysis, variance analysis, and significance tests, the primary and secondary factors influencing the rheological properties of coal-based solid waste filling slurry and their significance are evaluated. The order of primary and secondary influencing factors is determined as slurry concentration > cement addition > fly ash addition, and the order of effect significance is slurry concentration > cement addition > fly ash addition. The mass concentration of coal-based solid waste filling slurry is determined to be 75.2%, with the optimal ratio of cement∶fly ash∶coal gangue∶water as 12∶19.5∶43.7∶24.8. Secondly, a model for solid particle sedimentation based on the solid-liquid two-phase carrier suspension fluid is established for long-distance pipeline transportation of coal-based solid waste filling slurry. The density of the solid-liquid two-phase carrier suspension fluid is determined to be 1626.82 kg/m³, through the calculation of critical non-settling particle diameter mechanical model, granularity screening experiment, and rheological characteristic parameter test. The coal-based solid waste filling slurry is identified as an unstable slurry, lacking long-term suspension stability for long-distance pipeline transportation. Finally, the critical suspension yield stress value and critical suspension plastic viscosity value required for the coal-based solid waste filling slurry to transition into a suspension-stable slurry are determined to be 172.87 Pa and 2.39 Pa·s. A method is proposed to establish a stable slurry system for long-distance pipeline transportation of coal-based solid waste filling slurry by adding a suspending agent, with the aim of solving the practical engineering problems of long-distance filling mining of coal-based solid waste in coal mines.