Abstract: Zhongguan Iron Mine is expected to adopt the stage open stoping with subsequent filling，in which the reasonable determining of backfill strength is one of the key.Since various problems occur in the traditional method to determine filling strength，it′s necessary to explore a more scientific approach to seek for reasonable match between backfill strength and rock mass.Laboratory mechanics tests on tailing cemented backfill in Zhongguan Iron Mine were carried out，obtaining the stress-strain curves.Based on this，the damage constitutive models of the backfill body before peak stress were established by using the damage mechanics.According to the principle that the peak deformation energy of backfill should be corresponded to releasing energy from excavated rock mass，the optimum backfill strength and ratio of Zhongguan Iron Mine were determined as 1.86 MPa and 1∶6 respectively，which plays a significant role in baclfill mining production on site.

Key words: Backfill mining methods, Damage constitutive model, Backfill strength, Energy match, Cemented tailings backfill