Cemented backfill is undoubtedly affected by blasting disturbance when the pillar stopping of subsequent backfill of sublevel mining or stage mining in two steps. The mechanical properties of cemented backfill under dynamic loading are directly related to the safety of mine production. With the help of SHPB (split Hopkinson pressure bar), the uniaxial impact test of SHPB was carried out under high strain rate, the stressstrain curves of sized tailings cemented backfill under different strain rates were obtained, and the failure mechanism was analyzed. The results show that: ①Under the low average strain rate, strength of backfills dynamic strength increase factor is about 1.With the increase of the average strain rate, the dynamic peak stress becomes larger, and the dynamic strength increase factor increases; When the strain rate reaches 80-100 s-1, the dynamic strength increase factor is about 2, the maximum is more than 3.The two factors show a significant correlation. ②In a certain range, the dynamic peak stress of cemented backfill increases with the increase of concentration and proportion. ③Based on the comparison and analysis of the failure morphology of cemented tailings backfill with different strain rates, the maximum strain rate to maintain its macro stability is 50 s-1. Finally, the SHPB uniaxial impact process of backfills was simulated by using ANSYS/LSDYNA and the stress strain curve and the failure characteristics of backfills are in agreement with the experiment, which proves the correctness of the conclusion.