In experimentation of mining and filling,it was found that backfill with different apparent granulometric composition has different strength and volume-weight.The test and analysis of grain size indicated that different degrees of segregation once occurred on the backfill in different area of stope during filling,which has obvious difference in grain size.The backfill composed of finer particles has higher content of cement and higher uniaxial compressive strength,on the contrary,the backfill composed of coarser particles has lower content of cement and lower uniaxial compressive strength.The tested result of grain size distribution of backfill is well consistent with the tested results of its uniaxial compressive strength.