Abstract: To investigate the axial compression performance of T-shaped partially encased steel-concrete composite columns (T-shaped PEC columns), a finite element analysis model for T-shaped PEC columns subjected to axial loading is established using ABAQUS software, incorporating the complex nonlinear effects related to material properties, geometry and contact interactions. The accuracy is verified through a comparison with the existing experimental results. Subsequently, an extensive parametric analyses is conducted to examine the effects of steel plate thickness, transverse links spacing, limb height-to-thickness ratio, steel yield strength and concrete compressive strength on load capacity, ductility and concrete strength enhancement factor of the specimens. A comprehensive analysis of the entire axial compression process for a typical specimen is conducted, revealing the constraint mechanism among steel, transverse links and concrete, as well as examining the distribution of contact stresses and failure characteristics. Based on the concrete stress distribution in the cross-section of T-shaped PEC columns, the concrete section is divided into the un-effectively weakly confined zone, effectively weakly confined zone and strongly confined zone. The calculation method of concrete area in each zone is obtained by introducing the parameters of the transverse links spacing and the limb height-thickness ratio. Through strain compatibility and interface interaction analysis, the lateral confinement stress under peak load is calculated, leading to the establishment of a calculation method for the concrete strength in each zone and the axial compression capacity of T-shaped PEC columns. This study provides a scientific basis for establishing the design theory of T-shaped PEC columns.