An　effective　praseodymium　oxysulfate/Ba0.5Sr0.5Co0.8Fe0.2O3-delta　composite　cathode　with　high　stability　in　10%　CO2/air　was　investigated.　The　addition　of　50　vol.%　of　the　praseodymium　oxysulfate　shows　much　better　tolerance　to　CO2,　and　reduced　the　polarization　resistance　of　the　cathode　to　1/3　comparing　with　that　of　Ba0.5Sr0.5Co0.8Fe0.2O3-delta　(BSCF).　The　CO2-temperature　programmed　desorption　(TPD)　and　the　electrochemical　impedance　spectroscopy　(EIS)　proved　the　effectiveness　of　the　praseodymium　oxysulfate　phase　to　reduce　the　electrode　resistance　and　to　improve　the　CO2　resistance.　The　coefficient　thermal　expansion　(CTE)　rate　along　with　the　different　volume　percentage　of　praseodymium　oxysulfate　was　also　measured　and　it　was　found　that　the　praseodymium　oxysulfate　helps　to　regulate　the　total　CTE　of　the　composite　to　match　with　doped-ceria　electrolyte.　It　is　proposed　the　higher　acidity　of　Pr3+/4+　cations　inhibited　the　reaction　of　alkaline　earth　metal　oxide　to　form　carbonates　on　the　surface　of　the　BSCF　particles.　The　above　results　proved　praseodymium　oxysulfate/Ba0.5Sr0.5Co0.8Fe0.2O3-delta　to　be　a　highly　active　and　stable　cathode　for　solid　oxide　fuel　cells.