Abstract: According to the experimental investigation on the three small span-depth ratio ultrahigh toughness cementitious composite specimens and one ＲC coupling beam specimen under low cyclic reversed loading，the failure patterns and the mechanical behaviors of the coupling beam specimens such as load displacement hysteretic loops and strain of the steel were analyzed． It was also studied the effect of changing span-depth ratio of the specimens on seismic behavior of coupling beams． Test results indicated that the destroy mode of small span-depth ratio coupling beams due to their better toughness had the trend from brittleness to ductility; and the hysteretic loops of ultrahigh toughness cementitious composite coupling beam specimens showed a reversed S shape，but hysteretic loops were fuller than those of reinforced concrete coupling beam specimens． Steel bar yielded in the process of the test． Ultrahigh toughness cementitious composite can improve the seismic performance of coupling beams and meet the requirements of engineering design．