Abstract: The local-overall interactive buckling behavior of welded stainless steel box section columns was analyzed by using the finite element (FE) method in order to explore the plate post-buckling strength and achieve more economical and efficient sectional design. Elaborated FE models were developed to simulate the performed interactive buckling tests, taking account of the possible influences of nonlinear material properties, welding residual stresses, local and global geometric imperfections. Upon the validation of accuracy for the FE models, systematic parametric studies were carried out, generating supplemental numerical results. The obtained test and numerical results were compared with the theoretical calculation methods, indicating that the theoretical methods may provide overestimated predictions for the interactive buckling capacity. Modified calculation coefficients have been proposed for the austenitic and duplex stainless steel alloys, accompanied by a new direct strength method (DSM) formula, and their accuracy in predicting the interactive buckling capacity of welded stainless steel box section columns has also been verified by the obtained test and numerical results.