Abstract: A study was conducted to investigate the overall buckling behavior of partially encased composite (PEC) columns made of compact steel I-section under axial and eccentric loadings. A finite element model was set up to model the behavior of PEC columns and was validated by comparison with previous experimental data. This model is used to analyze the influence of parameters including longitudinal reinforcements, transverse links and section aspect ratios on the ultimate stability load of PEC columns. The overall stability factor of axially loaded PEC columns referring to axially compressive loaded steel members is selected through numerical computation by finite element analysis. The formulas for overall stability design of axial and eccentric compressions are proposed.