The past study indicates that, when the space joint of concentric annular-stiffer is loaded, stress concentration may generate at corner. The destruction usually concentrates in the joint region, and then cannot generate “strong joint”. To change this unfavorable characteristic, the reduced beam section connection is adopted. Through oriented reducing beam section, the plastic region is formed, which can achieve the aim of “weak beam, strong joint”. After the simulation and analysis to space joints on outer concentric annular-stiffer which are processed by reduced beam section, the loading conditions of the joints are obviously improved in the following aspects: (1) the stress distribution on annular plate is smoothed obviously, the degree of stress concentration on corner is significantly decreased; (2) to assure plastic hinge firstly appear on the beam end but not the ring surface, we can change the size of ring plate, length of beam and the flange weaken degree; (3)the joint stiffness does not decrease during the stage of elastic loading; (4)under repeated loading, the joint region has little change and the plastic expansion on the ring surface is not obvious. Above all, reducing beam section can improve the mechanical properties of CFST-steel beam space joints with outer concentric annular-stiffer, thus the “strong joint” requirement could be fulfilled.