CO2　air　source　heat　pump　(ASHP),　as　a　kind　of　clean　and　efficient　heating　equipment,　is　a　promising　solution　for　domestic　hot　water　and　clean　heating.　However,　the　promotion　of　CO2　ASHP　encounters　a　great　resistance　when　it　is　used　for　space　heating;　namely,　the　return　water　temperature　is　too　high　that　cased　higher　throttle　loss,　which　decreases　the　COP　of　the　CO2　ASHP　unit.　To　solve　this　problem,　a　heating　system　of　CO2　ASHP　coupled　with　thermal　energy　storage　(TES)　is　developed　in　this　work.　The　simulation　model　of　the　studied　system　is　established　using　TRNSYS　software,　and　the　model　is　verified　by　experimental　data.　Additionally,　the　performance　of　the　studied　system　is　optimized,　and　its　economy　is　analyzed　by　life　cycle　cost　(LCC).　The　results　showed　that,　compared　with　the　system　before　optimization,　the　cost　of　the　optimized　system　increased,　the　annual　operating　cost　of　the　system　was　reduced,　and　the　COP　of　the　system　(COPsys)　increased　by　7.4%.　This　research　is　helpful　in　improving　the　application　of　the　CO2　ASHP　unit　in　cold　server　and　cold　areas.