The objective of the study is to examine the quantitative influence of end friction on the dynamic mechanical behavior of concrete under medium and low strain rates. Considering the concrete heterogeneity, a mesoscale mechanical model was established to study the confinement effect of end friction, in which the concrete was assumed to be composed of aggregates, mortar matrix, and the interfacial transition zones between them. The friction behavior was utilized to describe the interaction between the concrete specimens and loading apparatus. The dynamic axial compressive mechanical behavior of concrete subjected to different medium and low strain rates and friction coefficients was simulated. Furthermore, the confinement mechanism of end friction on the compressive dynamic increase factor (DIF) of concrete was studied. The simulation results indicate that with the increase of end friction coefficient, the uniaxial compressive strength of concrete first increases and then becomes stable; the end friction confinement changes the local stress state and damage distribution of concrete, and it thus contributes to the increase in compressive strength of concrete; the friction contribution factor presents a descending tendency with increasing the strain rate and decreases obviously when the end friction coefficient increases.