Abstract: In order to meet the mine demand of cemented paste backfill for different size classification with high quality and low price，the effect of admixture of coarse，fine and ultra-fine limestone powder on the properties of cemented paste backfill was researched using the course and fine classified tailings cemented paste backfill as research objects.The test results showed that cemented paste backfill (CPB) would be formulated by the solid concentration of 65% fine classified tailings and solid concentration of 75% coarse classified tailings with the admixture 15% of ultra-fine limestone powder，by which slumps are all higher than 200 mm，water removal percentages are all lower than 2% and the 28 d unconfined compressive strengths (UCS) are 0.3~1.2 MPa and the 28 d sedimentation rates are lower than 2%.With the continuous increasing of ultra-fine limestone powder content，the slumps and water removal percentages decline，but the 28 d UCS slightly increase，and the sedimentation further decrease.How to increase the 28 d UCS of CPB would be the focus of the research in future.

Key words: Cemented paste backfill, Limestone powder, Slump, Water removal percentage, Compressive strength, Sedimentation rate