Abstract: In order to study the axial compression performance of composite long columns made of square steel tube filled with steel-reinforced recycled concrete. In this work, 18 finite element models of composite long columns are established in this paper. The relationship curves of load versus deflection in the middle column height, stress distribution rule and failure models of typical specimens were analyzed. The influence of slenderness ratio, recycled aggregate replacement ratio, steel tube thickness, recycled concrete strength grade and profile steel ratio on the mechanical properties of composite long columns under axial compression was considered. In addition, the practical bearing capacity calculation formula of composite long column under axial compression was obtained with the regression analysis method. The results indicate that recycled aggregate replacement ratio and slenderness ratio make little effect on bearing capacity of composite long columns under axial compression, while steel tube thickness, recycled concrete strength grade and profile steel ratio have significant effect on the bearing capacity of composite long columns under axial compression. Furthermore, the calculated value of the practical bearing capacity formula is in good agreement with the finite element value and the test value.