The　performance　analysis　and　optimization　of　an　air　heat　pump　are　carried　out　by　taking　the　heating　load　density　as　the　optimization　objective　in　this　paper.　Numerical　examples　show　the　effects　of　pressure　ratio　and　allocation　of　thermal　conductivity　on　the　heating　load　density　of　the　heat　pump.　The　results　obtained　are　different　from　those　with　the　heating　load　objective.　The　air　heat　pump　design　with　heat　loading　density　optimization　leads　to　a　smaller　size　of　each　equipment.