This article investigates the elastic compound buckling behavior of latticed columns with three lacing systems under two boundary conditions. Valid numerical method named SEM, that conducts buckling analysis using strain energy of bars and potential energy of chords, was built to address flexural, torsional, and flexural-torsional buckling loads along with their overall and local buckling deformations. Eurocode 3 and finite element software ABAQUS were used to validate the auxiliary of SEM. Through the research on X-lacing, E-lacing, and K-lacing latticed columns under two boundary conditions, the rigidity of bars was found to exceed a threshold value affecting the linear buckling load. When the cross-sectional area of lacing bars tends to 0 or threshold value, Eurocode 3 guidelines were imprecise in forecasting the linear buckling load. Eccentricity and geometric imperfections would decrease the buckling capacity of built-up columns substantially. The K-lacing columns respond more sensitively on local imperfections than the Xlacing and E-lacing columns under simply supported condition. However, for the columns under cantilever state, local imperfections have no significant impact for the three lacing columns. In addition, the numerical results of nonlinear buckling load and equilibrium path from SEM considering geometric imperfections are close to the output of finite element method, validating the accuracy of SEM.