Abstract: To study the axial compression bearing capacity of short welded steel tubes between sections of steel tube towers, six steel tube specimens were designed for each of the two welding processes of high-frequency welding and submerged arc welding respectively, and the axial compression loading was realized by 4-axis centering control technology. The feedback relationship between failure mode, strain distribution, bearing capacity and initial welding defects was analyzed. According to the characteristics of the initial defects of the two welding processes, the finite element models considering the initial defects of the welding are established respectively. The high-frequency welding considers the influence of initial bending and longitudinal residual stress. The submerged arc welding process also considers the influence of circumferential non-circularity based on the two kinds of defects. The comparison with measured data and the failure morphology verifies the accuracy of the finite element model. Finally, the slenderness ratio is taken as the main change parameter to extend the analysis and expand the depth and breadth of the test. The results show that: welding defects have a significant effect on the axial compression failure morphology of Q550 short steel tubes, and the local failure locations of the welded steel tube are all on the side of the weld, high-frequency welding is convex and submerged arc welding is sunken; the conformal mapping theory of complex function can be used as a universal method to provide a convenient way for finite element modelling to consider the effect of circumferential non-circularity of multi-pass submerged arc welding steel tubes.