Abstract: Twelve Y-eccentric braced steel frames were designed to complie with Chinese seismic code. The response modification factor R, overstrength factor Ω and redundancy factor Ω₃ of each building were evaluated by the capacity spectrum method combined with the global capacity envelops obtained from an improved pushover analysis. Moreover, the effects of storey numbers and spans of the structure on these factors were analyzed. The results show that the 20% elastic design earthquake action of Y-eccentric braced steel frames can be approximately reduced on the base of Chinese seismic code.