Abstract: In order to improve the dynamic properties and microstructure of ordinary cement stabilized soil, four kinds of modified cement stabilized soil samples with different contents of metakaolin were prepared under the action of alkali excitation reaction. The samples in curing process were subjected to separate Hopkinson pressure bar (SHPB) uniaxial compression, nuclear magnetic resonance (NMR) scanning and electron microscope scanning (SEM) tests. The results showed that the dynamic compressive strength of modified cement soil mixed with metakaolin increased first and then decreased with the increasing of metakaolin content, and the dynamic compressive strength reached the maximum when the metakaolin content was 4 %. The T2 curve of composite cement soil was bimodal distribution, and the main peak accounted for a large proportion, the proportion of P1 peak representing small pores was more than 80%, and the proportion of P2 peak representing large pores decreased with the increasing of curing time. The modification from metakaolin can promote the hydration reaction, and the filling effect from hydrated calcium silicate and ettringite makes density of the material significantly increased and the dynamic performance improved. The research results can provide reference for further resource utilization of metakaolin.