To study the seismic performance of partially encased composite columns with T-shaped sections (abbreviated as T- PEC columns), five T-PEC column specimens with different axial compression ratios and different construction of main steel components (MSCs) are tested subjected to the cyclic horizontal load. The five specimens included two specimens with MSCs of solid-web steel (abbreviated as SWS T-PEC column), and three specimens with MSCs of honeycomb steel (abbreviated as HS T-PEC columns). Combined with test and finite element (FE) analysis results, the impact of steel web opening and the axial compression ratio on the seismic behavior of T-PEC columns are investigated. The results indicate that all T-PEC column specimens failed near the column base, characterized by elastic-plastic buckling of the steel flange and adjacent concrete crushing, showing typical cross-section compression-bending failure mode. The load-displacement hysteresis curves of all column specimens were full, with the hysteresis loops at the same loading level almost coinciding, indicating good energy dissipation and load-bearing stability. SWS T-PEC column exhibited better deformability, ductility, and energy dissipation capacity compared to the HS T-PEC column under the same axial compression. Furthermore, the size of the web opening will affects the PEC column performance, while the shape and spacing of the web opening have little effect on the performance. As the axial compression ratio increased, the lateral stiffness and lateral resistance capacity of the PEC columns increased, but the deformability, ductility, and energy dissipation capacity decreased. Both full-section plasticity method and numerical integration method provided reasonably accurate estimate on the flexural capacity of the section of the T-PEC columns under the action of compression-bending load.