Compared　to　conventional　proton　exchange　membrane　(PEM)　fuel　cell　with　thick　membrane　electrode　assembly,　today＇s　automotive　PEM　fuel　cell　adopts　thin　MEA　with　thin　catalyst　coated　membrane　(CCM).　The　objective　of　this　modeling　study　is　to　shed　light　on　PEM　fuel　cell　with　thin　MEA　under　low　humidity　operation　condition.　The　effects　of　cathode　catalyst　oxygen　reduction　reaction　activity　and　local　O-2　transport　resistance　on　automotive　PEM　fuel　cell　high　current　operation　are　elucidated.　The　local　O-2　transport　resistance　is　found　to　have　large　impacts　on　limiting　current　density.　The　effects　of　cathode　humidifier　elimination,　operating　pressure,　and　stoichiometry　ratio　on　PEM　fuel　cell　performance　are　also　discussed.　The　thin　membrane　in　thin　MEA　has　much　lower　ohmic　resistance　compared　with　thick　membrane,　and　it　is　easy　to　be　hydrated　under　low　humidity　condition.　But　H-2　crossover　is　stronger　for　thin　membrane　and　needs　to　be　watched　out　when　thinning　the　membrane.　In　addition,　a　50　cm(2)　PEM　fuel　cell　with　counter-cross　flow　field　is　simulated　for　demonstration　of　medium　scale　PEM　fuel　cell　modeling.　Under　0.65　V　and　50%4%　humidity　operating　conditions,　the　50　cm2　PEM　fuel　cell　is　predicted　to　supply　average　current　density　of　2.51　A/cm(2).