<p>In order to reduce the segregation degree of cemented backfilling slurry in coal mine and enable cemented backfill in coal mine (CBCM) to normally exert its load-bearing capacity, uniaxial compressive strength test, static segregation index test and microscopic properties test were carried out. The effect of suspending agent content (SAC) on the strength, static segregation index and microscopic properties of CBCM was discussed. The relationship between static segregation index and microscopic properties and backfill strength was analyzed. The results show that when SAC increases from 0 to 0.06%, the backfill strength increases first and then decreases, the static segregation index of backfilling slurry decreases by 46.81%, and the Ca(OH)₂ content in backfill decreases by 24.51%. The increase of SAC can improve the strength of CBCM, reduce the segregation degree of backfilling slurry and reduce the hydration products inside the backfill. The backfill strength increases first mainly because SAC reduces the segregation degree of backfilling slurry, and the backfill strength decreases later mainly because SAC inhibits the hydration reaction inside the backfill.</p>