[Objective]: Given that the mechanical behavior and failure mechanisms of double steel column embedded column base joints remain unclear, this study conducted experimental investigations and numerical simulations to comprehensively analyze their load-bearing mechanisms, failure modes, and mechanical responses. [Methods]: Based on the typical configuration of double steel column embedded column base joints at Guangzhou Baiyun Station, a 1:5 scaled specimen was designed according to similarity criteria for quasi-static loading tests. A three-dimensional nonlinear finite element model was established using ABAQUS, incorporating the Concrete Damage Plasticity (CDP) constitutive model and a refined mesh generation method. Comparative analyses were performed between experimental and numerical simulation results regarding load-displacement curves, stress distribution patterns, and concrete damage propagation paths, thereby elucidating the joint's load-bearing mechanisms and failure modes. Strain responses were systematically monitored for steel column components, concrete footings, reinforcing bars within the footings, and embedded steel tubes. [Results]: The research results indicate that the joint's failure mode is shear-compression failure of the concrete cap, while the steel column does not yield or experience buckling failure. [Conclusions]: (1) The failure of the double steel column embedded joint is dominated by shear-compression failure of the concrete cap. Its bending resistance is significantly better than its shear resistance, so priority should be given to improving the stirrup reinforcement ratio of the concrete cap and the arrangement density of shear studs on the steel column during design. (2) The double steel column and embedded circular steel tube form a multi-path load-transfer system through collaborative interaction, significantly enhancing the ultimate bearing capacity compared to traditional single steel column embedded joints. (3) The finite element method based on the CDP model and refined mesh division can effectively predict the mechanical behavior of the joint, providing a valuable reference for the optimal design of similar joints.