There is less research on the mechanical behavior of cement-based materials containing superabsorbent polymers (SAP) under high strain rate. In this paper, the total porosity and macroscopic pore (>100 μm) porosity of cement-based materials containing SAP were investigated by the use of mercury intrusion and graphical techniques. The effects of SAP particle size and extra water on the quasi-static (10-5 s-1) and dynamic (60~110 s-1) mechanical properties of the modified materials were analysed. Based on the study of the crack propagation behavior, the damage behavior of the cement-based materials was analyzed under high strain rates. The results show that the addition of extra water and the increase of SAP particle size improve the total porosity and macroscopic pore porosity of the materials, which reduce the compressive strength and elastic modulus of the specimens under quasi-static and dynamic compression. The addition of extra water and the increase of SAP particle size also enlarge the compressive strength dynamic increase factor and elastic modulus dynamic increase factor of the cement-based materials, which is due to the fact that an increase in total porosity and macroscopic pore porosity induces a change in the crack extension path, an increase in fragmentation, and a delay in the strain response.