Abstract: The static behavior of chevron brace when its beam is designed by a smaller unbalanced force is reviewed and it is revealed that the post-buckling behavior is fully dependent on the capacity of beam carrying unbalanced force. Lateral force-drift angle curves of dual systems composed of frame and chevron brace with their lateral capacity ratios of 1∶1 and 1∶3 are introduced, the capacity of the beam in chevron brace can carry 1.0 and 0.3 times the codified unbalanced force, respectively, totally 4 series of examples. Because the drift angles at brace buckling, tension yielding and frame lateral mechanism increase in order, brace buckling occurs first and then its capacity deteriorates, but the capacity of the frame develops and compensates the decrease of the compressive brace force, the total lateral capacity of the system after brace buckling depends on both the frame/brace capacity ratio and the capacity of the beam in chevron brace carrying unbalance force in chevron brace. Under the demand of assuring the total deteriorating percentage less than 20%, a relation between the frame/brace capacity ratio and the unbalance force ratio ratio is proposed.