Thermodynamic　optimization　of　an　irreversible　air　heat　pump　with　variable-temperature　heat　reservoirs　and　hot-　and　cold-side　counter-flow　heat　exchangers　has　been　studied.　The　expressions　of　the　heating　load,　the　exergetic　efficiency　and　the　ecological　function　of　the　heat　pump　cycle　are　derived.　Performance　comparisons　among　exergetic　efficiency　optimization,　ecological　optimization　and　traditional　heating　load　optimization　objectives　are　done.　The　effect　of　the　pressure　ratio　of　the　compressor,　the　allocation　of　heat　exchanger　inventory　and　the　heat　capacity　rate　matching　between　the　working　fluid　and　the　heat　reservoirs　on　the　optimal　performance　of　the　cycle　has　been　investigated　by　detailed　numerical　examples.　When　the　performance　optimization　of　the　cycle　is　carried　out　by　selecting　the　pressure　ratio,　three　optimization　objectives　give　simultaneously　attention　to　the　coefficient　of　performance　(COP).　The　pressure　ratio　should　be　the　one　that　is　little　bigger　than　the　optimum　pressure　ratio　corresponding　to　maximum　COP,　however,　the　results　of　three　optimization　objectives　are　consistent　by　optimizing　the　allocation　of　heat　exchanger　inventory　and　optimizing　the　heat　capacity　rate　matching　between　the　working　fluid　and　the　heat　reservoirs.　The　optimum　allocations　of　heat　conductance　are　close　to　each　other,　and　they　are　all　less　than　0.5.　The　results　may　provide　guidelines　for　the　design　and　optimization　of　practical　air　heat　pump　plants.