The　performance　analysis　and　optimisation　of　endoreversible　simple　air　heat　pump　with　constant-temperature　heat　reservoirs　is　carried　out　by　using　finite-time　thermodynamics.　The　expressions　of　the　heating　load,　the　exergetic　efficiency　and　the　ecological　function　of　the　cycle　are　derived.　The　influences　of　the　pressure　ratio　of　the　compressor　and　the　allocation　of　heat　exchanger　inventory　on　the　optimal　performance　of　the　cycle　are　investigated　by　detailed　numerical　examples.　Performance　comparisons　among　exergetic　efficiency　objective,　ecological　objective　and　traditional　heating　load　objective　are　performed.　The　results　may　provide　guidelines　for　the　design　and　optimisation　of　practical　air　heat　pump　plants.