Abstract: The influence of diagonal reinforcement, slab and axial force on the seismic behavior of coupling beams is examined through nine RC specimens, as well as the associated slab damages. The failure modes of all specimens are classified into two types, i.e. the shear failure and the flexure-shear failure. The yield strength and ultimate strength of specimens with diagonal reinforcement are both larger than those without diagonal reinforcement. The ultimate strength increases by more than 20%. The slab has a modest impact on the yield strength with an increase between 6% and 12%, but has little influence on the ultimate strength due to the shear failure. The crack width of slab reaches 0.2mm, the criterion of serviceability limit state, when the rotation is 0.25%, implying serious damage to slabs. Axial force exists during the test, and the axial compression ratio varies from 5% to 10%.