Abstract: In order to quantitatively describe the damage degree and failure process of the cemented backfill under dynamic load, numerical simulation software was used to perform SHPB dynamic impact on the cemented backfill, and the feasibility of the numerical simulation method was verified by the indoor SHPB impact test results. For 4 kinds of cemented fillings (with cement-sand mass ratios of 1∶4, 1∶6, 1∶8 and 1∶10 respectively) made under different impact speeds (1.5, 1.7, 1.8, and 2.0 m/s), the micro-crack density method was used to define the damage variable value d, and a numerical simulation study of the damage law and the failure process was conducted. The results are as follows. The wave shaper can be used in the numerical simulation to obtain a more ideal rectangle wave, making the stress on the same plane element of the specimen uniform without stress concentration. The numerical simulation results show the dynamic failure process of the cemented filling body, and the overall failure trend is that the edge peels off and the crack extends to the inside. In the process of increasing the loading speed from 1.7 m/s to 1.8 m/s, the damage variable increases by more than 10%; during the process of increasing the impact speed from 1.5 m/s to 2.0 m/s, the variation ranges of the damage variable d of the cemented filling body with the cement-sand mass ratios of 1∶4, 1∶6, 1∶8 and 1∶10 are 0.238～0.336, 0.274～0.413, 0.391～0.547, and 0.473～0.617, respectively. When the lime-to-sand ratio changes from 1:6 to 1:8, the damage “jumps” remarkably.