Abstract: The strength of cemented backfill is one of the most important factors determining the stableness of backfill body.Existed studies have found that once backfill slurries have been placed into stopes, the content and properties of porous water in cemented backfill materials can affect the migration of hydration ions of binders and the sulphate ions of outside environment, and then affect the strength of cemented backfill.To study and investigate the influence of backfill materials properties on porous water features, the porous water volume content in backfill materials and porosities of cemented backfill have been tested, and the relations between the two properties have been analyzed.The results show that after bleeding, there are still a huge amount of volume of backfill materials are porous water.The higher the concentration is, the higher the volume content of pore water is, and the range of different initial concentrations of backfill slurries is up to 16.90%.After curing, the porosities of cemented backfills are all lower than the pore water volume content of backfill materials with the same concentration.The range of porosities of different cured samples is 9.64%, which is almost decreased by nearly half comparing to the range of pore water volume content.Because of the increase of backfill concentration, the porosity will decrease, the connections of pores will be worse either, which can hinder the migration of pore water and result in the larger volume of air phase in cured cemented backfill.