In order to investigate the dynamic mechanical properties of roller compacted concrete, a series of dynamic compression tests have been carried out on roller compacted concrete cylindrical specimens with different diameters by the split Hopkinson compression bar(SHPB). The test results show that the roller compacted concrete material has a significant strain rate effect, as well as size effect, despite the dispersion of test results at high strain rates. That is to say, for the specimens with same size, the dynamic compressive strength increases with increasing strain rate, and the compressive strength enhancement increases with increasing specimen size when subjected to same loads. Moreover, recent studies have revealed that the above dynamic compressive strength enhancement is mainly the result of the coupling effect of strain rate effect due to material properties(namely true strain rate effect), lateral inertia effect, and end friction effect. It is of great significance to figure out the true strain rate effect of roller compacted concrete material for the better prediction of the dynamic response of roller compacted concrete structures under impact load. Based on the assumption that the real strain rate effect, lateral inertia effect and end friction effect are not related to each other, this paper quantitatively evaluates the enhancement of compressive strength caused by the lateral inertia and end friction constraints effect by numerical simulation and semi-theoretical derivation. Then the dynamic compressive strength enhancement is eliminated, and the true strain rate effect of roller compacted concrete material is obtained by the regression analysis of the corrected DIF data. The results show that the obtained true strain rate effect of roller compacted concrete is relatively close to the model proposed by Fib code and Hao.