An　air　source　heat　pump　(ASHP)　with　refrigerant　injection　is　proposed　for　the　air　conditioning　system　of　electric　vehicles　(EVs),　especially　for　efficient　heating　in　cold　winter,　when　there　is　no　wasted　heat　of　engines.　The　simulation　model　is　built　with　the　framework　of　two-phase　fluid　network,　where　the　compressor　is　separated　as　two　compressors　and　the　economizer　is　treated　as　two　heat　exchangers　in　the　injection　path　and　the　main　refrigerant　path.　With　the　validated　simulation　model,　the　heating　performance　is　analyzed,　and　the　results　show　that　the　coefficient　of　performance　(COP)　of　ASHP　with　refrigerant　injection　is　higher　than　1.4　and　the　discharge　temperature　is　less　than　100　when　the　outdoor　temperature　is　-20　.　The　above　performance　ensures　that　the　air　conditioning　system　and　EVs　can　operate　normally　with　high　efficiency　even　in　the　cold　winter,　which　is　much　helpful　for　the　practicability　of　EVs.　©　2018,　Editorial　Department　of　Transactions　of　NUAA.　All　right　reserved.