Abstract: Cement-soil composite pile is often utilized as the foundation of offshore bridges or wind turbines to resist lateral vibrations in natural environments. A mathematical model is proposed for the coupled vibration of the cement-soil composite pile and the soil around the pile under lateral dynamic loads through theoretical derivation. Then, the analytical expressions for the horizontal and rocking dynamic impedances at the pile head are obtained through theoretical derivation. Finally, the influence of cement-soil parameters on the dynamic impedance are studied through numerical calculation and parametric analysis. The results reveal that the increase of the cement-soil radius will increase the horizontal and rocking dynamic impedances, but it is not conducive to the horizontal dynamic impedance at high frequency vibration. The cement-soil depth should not exceed its effective reinforcement depth. The increase of the cement-soil elastic modulus is beneficial to improve the dynamic impedance of pile head.