The　open-cathode　design　with　simultaneously　integrated　air　supply　and　coolant　flow　systems　can　significantly　simplify　the　structure　of　proton　exchange　membrane　fuel　cell　(PEMFC).　Typically,　the　performance　of　open-cathode　PEMFC　system　is　highly　influenced　by　temperature　and　oxygen　excess　ratio　which　can　be　regulated　by　the　air　flow　fan.　The　axial　air　flow　fan　is　the　only　actuator　which　is　responsible　for　the　oxygen　supply　to　the　cathode　and　cooling　air　at　the　same　time.　In　this　study,　oxygen　mass　flow　rate　across　cathode　channels　is　regarded　as　the　only　control　variable　of　the　open-cathode　FC　system.　Air　flow　is　regulated　based　on　a　set　of　optimal　oxygen　excess　ratios　in　different　stack　currents　for　power　optimization　and　overheating　protection.　However,　the　air　flow　rate　is　determined　through　a　sensor　installed　to　measure　the　air　flow　rate　in　the　cathode　channels.　The　control　strategy　simultaneously　focuses　on　performance　optimization　with　overheating　protection　and　air　starvation　prevention,　whereas　the　fuel　cell　operates　its　full　range.　The　efficacy　of　the　proposed　method　and　control　is　verified　through　experiments　with　a　small　open-cathode　fuel　cell　system　with　a　real-time　platform　of　NI　(National　Instruments)　devices.