In this paper we try to tailor the chemical stability of cobalt-rich perovsldte Ba0.5Sr0.5Co0.8Fe0.2O3-delta (BSCF) by B-site doping Sb. The chemical stability of Ba0.5Sr0.5Co0.8Fe0.1Sb0.1O3-delta (BSCFS) was investigated by studying the oxygen nonstoichiometry, crystal structure and oxidation state by means of coulometric titration, high temperature X-ray diffraction (HT-XRD) and soft-X-ray absorption spectroscopy (s-XAS) in Various oxygen pressure (p(O-2)) and temperatures. The results prove that chemical stability of BSCFS is successfully improved in intermediate temperature solid oxide fuel cell working condition owing to Co valence change which is controlled by high valence cation doping. (C) 2016 Elsevier B.V. All rights reserved.