Abstract: In order to reduce the influence of slurry pipeline necking on overburden separation slurry filling work，the mechanism of pipe internal diameter reduction was analyzed，and related experiments and engineering practices were carried out to explore the prevention measures of slurry pipeline necking and pipeline attachment softening and dredging scheme.The results show that there are three main types of pipe diameter reduction: attachment type，deposition type and comprehensive type.The main types of pipe diame⁃ ter reduction are attachment type and deposition type.It can reduce the diameter of attachment type by im⁃ proving the smooth degree of pipeline，improving the composition of fly ash，increasing the pressure of slur⁃ ry transport，continuous slurry transport and regular flushing of pipeline，which also has a certain effect on the deposition type.0.25 mol/L acetic acid solution can be used as solvent to clean and dredge the slurry pipeline，and the effect is good.Through the above measures，the diameter reduction of slurry pipeline can be reduced to ensure the smooth progress of overburden separation slurry filling work.

Key words: overburden separation slurry transport, slurry material, diameter reducing, green mining