To replace full penetration weld with twin fillet weld for the design and construction of joint of beam to CFST (concrete-filled steel tube) column with interior strengthening ring, six specimens were tested by incremental loading and cyclic loading. The finite element package ANSYS was used to study the nonlinear behavior of such specimens. The finite element model was validated by comparing the computed values with experimental results. The failure mode was local buckling in the flange edge between beam flange and steel tube because of local stress concentration. When the joint was damaged, the stress of weld (including full penetration, partial penetration, and twin fillet weld) between steel tube and interior strengthening ring is smaller than yield strength. The twin fillet weld was proposed for design and construction of the joint instead of full penetration weld.