Abstract: In order to solve the problem of spatiotemporal interference between mine filling and coal mining, safe and efficient filling and mining of mines can be realized. Combined with the production system and mining conditions of Lijiagou mine, the non-cemented paste filling technology of floor drag pipe between the goaf was developed. In order to ensure the feasibility and basis of this technology, a physical model of non-cemented paste interframe floor drag pipe filling goaf was established, and non-cemented paste filling materials were prepared by using gangue and fly ash as aggregates, and the interaction between maximum particle size and mass concentration on the flow characteristics of slurry goaf was analyzed. The results show that: (1) the filling amount of slurry is mainly affected by the particle size of gangue, and the mass concentration mainly affects the diffusion rate of slurry in the goaf; (2) With the increase of slurry filling, the voids in the goaf gradually tend to be saturated, and the permeation mode shows a hemispherical diffusion distribution with the nozzle as the spherical center; (3) The simulation test revealed the mechanism of slurry flow diffusion and obstruction in the goaf area; (4) The sections are cut sequentially along the pipeline trend, and the gangue gradation and mass concentration in the slurry have obvious separability.