A new type of backfill materials using recycled brick and concrete waste as fine aggregates was designed with three cement-to-sand ratios (C/Sa) and five fly ash-to-sand ratios (FA/Sa). A series of measurements were conducted to investigate the fluidity and bleeding and mechanical properties including uniaxial compressive strength, stress-strain relationship, constitutive relation model and elastic modulus. The results showed fluidity had linear correlation on water-to-solid ratios(W/So); the range of the bleeding rates was in 4%~8% when the fluidity was within 200~250 mm. The compressive strengths had an exponential relationship to the cement-to-sand ratios and water-to-solid ratios. A constitutive relation model was put forward to describe the stress-strain relationship curve of backfill material on the base of the model of the concrete. The relationship between the unconfined compressive strength and elastic modulus was established, which could be used to calculate the modulus of backfill materials by the compressive strength directly.