An experimental investigation was conducted to investigate the axial compressive behavior of square longitudinal-seam steel tubular (LSST) stub columns with artificial crack defect in weld. The axial compression tests were carried out on 108 square LSST stub columns with crack defect and 3 square LSST columns without crack defect as control groups. The effect of design parameters such as thickness of tube, length and width of crack defect, location of crack defect on axial compressive behavior of square LSST columns were analyzed. Test results involved failure modes, load-displacement behavior, ultimate strength, initial stiffness, and ductility coefficient of all specimens were presented. The corresponding FE models of square LSST columns with crack defect are established and validated by comparison with experimental results. Test results have demonstrated that crack defect often led to stress concentration, causing significantly higher strain intensity at the position of crack defect compared to other areas. Square LSST columns with crack defect exhibited a 26% lower ultimate strength at T = 2.5 mm. The ductility coefficient enhanced with the decrease of length and width of crack defect. However, the location of crack defect had limited effect on axial behavior of LSST columns. In addition, parametric formulae of ultimate strength for square LSST columns with crack defect are proposed, which achieved high accuracy. The research results could provide evaluation reference in design and construction of LSST column.