This　study　has　deduced　a　simple　method　about　calculating　piston　wind　speed　and　airflow　distribution　by　a　quasi　one-dimension　numerical　model.　It　also　has　found　the　influence　factor　of　piston　effects　such　as　train　speed,　the　frontal　area　ratio　of　train　to　tunnel,　tunnel　length　and　so　on.　In　order　to　verify　the　feasibility　of　the　method,　this　study　used　the　authoritative　subway　environmental　simulation　(SES)　computer　program　to　simulate　the　piston　effects.　The　simulation　results　show　that　the　air　speed　and　flux　distribution　are　very　important　design　parameters　for　ventilation　by　piston　effects　for　subway　tunnel　system.　©　2009　ASCE.