Abstract: The dynamic compressive properties of mortar material at different strain-rates are experimentally investigated by split Hopkinson pressure bar (SHPB) test, in which the relationship between the dynamic increase factor (DIF) and strain-rate is obtained. Numerical simulations using a simplified model are conducted based on the strain rate curve obtained from experiments. The principle of the unavoidable inertia effect known as the "structure effect" in dynamic compressive tests is discussed. To obtain the inherent DIF of mortal material subjected to high strain-rate, numerical simulations are conducted to eliminate the inertia effect. It is found that the predicted stress-strain curves in the numerical simulation agree well with the corresponding experimental data when the above-mentioned inherent DIF is used as the numerical input. Furthermore, the superiorities of the proposed inherent DIF are validated by comparing the CEB recommended DIF and existing semi-empirical DIF as the numerical inputs.