Abstract: To improve the seismic performance of reinforced concrete (RC) pier column and fully utilize the mechanical properties of engineered cementitious composites (ECC), an innovative ECC shell-RC composite pier column was proposed. The numerical analysis model of the composite pier column was established and verified based on ABAQUS platform and existing experimental results, respectively. On this basis, the influence of common design parameters on the seismic performance of the composite pier column was systematically investigated, including the ECC segment height, ECC shell thickness, longitudinal reinforcement ratio, volume stirrup ratio and axial compression ratio. Finally, the plastic hinge development mechanism of the composite pier column was clarified. The results show that compared with RC pier column, the bearing capacity, displacement ductility and energy dissipating capacity of ECC shell-RC composite pier columns are improved. The peak loads of the composite pier columns increase with the ECC segment height increasing. The seismic performance of the composite pier columns can approach to that of the ECC pure pier column when the height of the ECC shell-RC composite segment is larger than 1.4h (Transverse dimension of the pier column h). The peak load and ductility of the composite pier column increase with the ECC shell thickness and longitudinal reinforcement ratio increasing. However, the seismic performance of the composite pier column will not significantly change when the ECC shell thickness is larger than 1/5h. The increase of the axial compression ratio can increase the initial stiffness and peak load of the specimen, while has a negative impact on its ductility. The decreasing of the volume stirrup ratio around the plastic hinge zone will significantly decrease the ductility of the specimen, but little affect its bearing capacity. The plastic hinge development mechanism of the composite pier column is significantly influenced by the height of the ECC shell-RC composite segment. There is a minimum critical height of the composite segment to make the plastic hinge zone not transfer.