For high-rise buildings, partially encased concrete columns (PEC columns) are ideal edge restraint members. In order to explore the structural mechanical properties of steel frame structure with PEC columns, 12 models of steel frame structure with PEC columns on 8 floors and 12 floors are established by using OpenSees finite element software, and Pushover analysis is carried out. Through software simulation analysis, the effects of the grade of concrete filled in PEC column and the thickness of section steel plate on the mechanical properties of the overall structure are obtained. The analysis shows that pouring concrete into the section steel column improves the lateral stiffness, ductility and bearing capacity of the structure, and the influence of the change of relevant parameters of PEC column on the bottom of the structure is greater than that on the top of the structure.