As a highly efficient energy conversion device, proton-conducting solid oxide fuel cells (PCFCs) have attracted intensive attention. Unfortunately, its practical application is limited by the catalytic activity and stability of the cathode. Here, we report a novel electrochemical catalyst of 10 mol.% La modified Ba0.5Sr0.5Co0.8Fe0.2O3-? cathode, showing much improved stability under typical PCFCs working conditions. XRD patterns confirm that La0.1Ba0.4Sr0.5Co0.8Fe0.2O3-? maintains cubic structure after treated in humid air or 10% H2O - 90% N2. In addition, La0.1Ba0.4Sr0.5Co0.8Fe0.2O3-? also demonstrates outstanding oxygen transport properties with a chemical surface exchange coefficient of 2.3∗10-3 cm s-1 at 700 ?C, and the assembled single cells using this novel material present a minimal polarization resistance of 0.05 ? cm2 at 700 ?C. The high stability and great electrochemical performance of La0.1Ba0.4Sr0.5Co0.8Fe0.2O3-? may result from the stronger interaction in the La-O bond than in Ba-O. This work provides a strategy to modify materials properties via optimizing the interaction between metal and oxygen ions in the oxide lattice.