The pillar blasting stope project of 425 m medium stage in Lilou Iron Mine of Minmetals Mining was presented.Based on the stress wave theory,the propagation of blasting stress wave in total tailing cemented backfill and its interaction with medium interface were analyzed.According to the different failure criteria and mechanism of backfill,such as impact-compression-shear,shear and reflective tension,the particle vibration velocity threshold of backfill were studied.The research shows that the cementing surface between the pillar and the 1∶8 ratio backfill is prone to shear failure due to blast stress wave,and the cemented backfill is prone to compression-shear failure.Under the action of refracted and reflected stress wave,the cementing surface between the 1∶8 ratio and 1∶20 ratio backfill is prone to tensile failure,and the spall fracture of the 1∶8 ratio backfill adjacent to the 1∶20 ratio backfill may occur.The specific particle vibration velocity threshold of the backfill is summarized below:The particle vibration velocity threshold of shear failure on the cemented surface between the pillar and the 1∶8 ratio backfill is 27.6 cm/s;the particle vibration velocity threshold of compression-shear failure of 1∶8 ratio backfill adjacent to pillar is 172 cm/s;the particle vibration velocity threshold of tensile failure on the cementing surface between the 1∶8 ratio and 1∶20 ratio backfill is 12.6 cm/s.the particle vibration velocity threshold of spall fracture of the 1∶8 ratio backfill adjacent to the 1∶20 ratio backfill is 52.6 cm/s.