Seismic behaviors of the nine coupling beam specimens that three-layer-closed-restraining stirrups arranged in the coupling beam section depth direction were investigated experimentally. Effects of span-to-depth, amount of stirrups and longitudinal bars of coupling beam on its failure mode are studied, as well as the hysteretic behavior, stiffness degradation, and deformation capacity. Coupling beams with span-to-depth ratio of 0.75－1.5 were observed to suffer shear failure or flexural-shear failure, no matter whether longitudinal reinforcements yield or not. The existing of three-layer-closed-restraining stirrups along the section depth of coupling beam effectively improved its deformation and energy dissipation capacity. According to the experimental results, the formulae for estimating shear strength of the coupling beams were suggested considering the effect of longitudinal reinforcements. Estimated shear strength of coupling beams agreed well with the experimental data.