Abstract: In order to find out cheap and feasible backfill material, the loess, as raw material, is used to produce cementitious backfill material, and the strength of the material is determined by different factors. The results show that the strength of the material is relating with several factors. Along with the increase of cement proportion, mass concentration and fly ash proportion, the strength increases gradually. The strength deceases when the sand proportion increases slowly. But the impact on strength is not significant from lime and gypsum. The sensitivity of strength response is different to the factors, and the sensitivity of mass concentration is the most powerful, the sensitivity of fly ash is the weakest.