This　study　used　a　three-dimensional　numerical　model　of　a　proton　exchange　membrane　fuel　cell　with　five　types　of　channels:　a　smooth　channel　(Case　1);　eight　rectangular　baffles　were　arranged　in　the　upstream　(Case　2),　midstream　(Case　3),　downstream　(Case　4),　and　the　entire　cathode　flow　channel　(Case　5)　to　study　the　effects　of　baffle　position　on　mass　transport,　power　density,　net　power,　etc.　Moreover,　the　effects　of　back　pressure　and　humidity　on　the　voltage　were　investigated.　Results　showed　that　compared　to　smooth　channels,　the　oxygen　and　water　transport　facilitation　at　the　diffusion　layer-channel　interface　were　added　11.53%-20.60%　and　7.81%-9.80%　at　1.68　Acm(-2)　by　adding　baffles.　The　closer　the　baffles　were　to　upstream,　the　higher　the　total　oxygen　flux,　but　the　lower　the　flux　uniformity　the　worse　the　water　removal.　The　oxygen　flux　of　upstream　baffles　was　8.14%　higher　than　that　of　downstream　baffles,　but　oxygen　flux　uniformity　decreased　by　18.96%　at　1.68　Acm(-2).　The　order　of　water　removal　and　voltage　improvement　was　Case　4　＞　Case　5　＞　Case　3　＞　Case　2　＞　Case　1.　Net　power　of　Case　4　was　9.87%　higher　than　that　of　the　smooth　channel.　To　the　Case　4,　when　the　cell　worked　under　low　back　pressure　or　high　humidity,　the　voltage　increments　were　higher.　The　potential　increment　for　the　back　pressure　of　0　atm　was　0.9%　higher　than　that　of　2　atm　(1　atm　=　101.325　kPa).　The　potential　increment　for　the　humidity　of　100%　was　7.89%　higher　than　that　of　50%.