Due　to　modern　lifestyles,　commercial　streets　have　become　an　indispensable　place　in　urban　life.　Pedestrian　wind　environment　is　one　of　the　primary　concerns　in　commercial　street　design　since　it　has　direct　influences　on　urban　heat　island　effect,　indoor　and　outdoor　thermal　comfort,　outdoor　air　pollution　and　indoor　air　quality.　To　investigate　pedestrian　wind　environment　of　a　commercial　street,　a　case　study　was　performed　on　Beijing　Wangfujing　Commercial　District　in　China　and　Tokyo　Sensoji　Temple　District　in　Japan　separately.　First,　the　original　models　of　these　two　commercial　streets　were　established　based　on　real　streetscapes　and　the　surrounding　buildings.　The　velocity　filed　under　typical　summer　climatic　conditions　was　then　output　to　assess　the　wind　environment　of　each　street.　The　results　show　that　pedestrian　wind　environment　under　the　current　design　is　not　comfortable　for　Beijing　street　and　Tokyo　street.　To　improve　this　situation,　further　work　was　conducted　on　optimization　of　current　street　design,　specifically　on　the　determination　of　a　suitable　aspect　ratio　H/W　(W　is　the　width　of　the　street　and　H　is　the　height　of　the　street　buildings).　In　this　step,　simplified　models　derived　from　original　models　of　each　street　were　used　for　simulation.　According　to　present　simulation　results,　the　determined　aspect　ratio　H/W　is　about　0.80　and　0.30　for　Beijing　street　and　Tokyo　street,　respectively.　It　should　be　noticed　that　this　ratio　could　differ　on　the　height　of　the　street　buildings　as　well　as　on　the　climatic　condition　of　the　street　locations.　©　2020,　Springer　Nature　Singapore　Pte　Ltd.