Degradation　phenomena　is　the　key　factor　restricting　the　performances　of　Proton　Exchange　Membrane　Fuel　Cell　(PEMFC)　in　its　whole　life　period.　This　paper　presents　a　degradation　model　for　predicting　the　lifetime　and　degradation　progress　of　PEMFC　stack.　The　thermodynamic　and　economic　performances　of　PEMFC　stack　over　the　lifetime　are　conducted.　In　thermodynamics,　the　transient　voltage,　degradation　rate,　electrical　power　and　efficiency　at　various　working　current　are　discussed.　In　economics,　the　fuel　consumption,　effects　of　fuel　price　and　degradation　rate　on　total　cost　of　PEMFC　stack　during　the　whole　lifetime　are　studied.　The　results　show　that　high　working　current　accelerates　the　cell　degradation,　largely　shorten　the　lifetime　of　PEMFC　stack.　With　the　raise　of　current,　the　degradation　rate　of　singe　cell　climbs　to　4.87　?　10-5V　h-1,　lifetime　shorten　by　25.9%.　The　electrical　efficiency　of　PEMFC　stack　at　80A　can　reach　38.3%.　Furthermore,　with　the　raise　of　degradation　rate,　the　fuel　consumption　and　total　cost　increases,　the　average　cost　of　PEMFC　stack　fluctuates　from　17.6　to　34.5　$　h-1.