Subways　and　buses　are　two　primary　modes　of　the　public　transit　system.　In　order　to　decide　the　reasonable　price　ratio　of　the　subways　and　the　buses,　the　effects　of　fare　on　traffic　structure　is　studied　in　this　paper.　Questionnaire　investigations　of　public　traffic　mode　split　were　done　in　Beijing.　Influencing　factors　of　selecting　subways　and　buses　were　analyzed.　The　results　show　that　trip　time,　cost,　gender,　age,　occupation,　income,　and　trip　intention　have　remarkable　influences　on　the　results　of　trip　mode　split.　On　the　basis　of　combination　of　variable　factors,　the　variables　that　should　be　used　in　the　model　were　determined　and　the　model　of　public　traffic　mode　split　based　on　disaggregate　model　is　given　in　this　paper.　The　relationship　between　fare　and　mode　split　is　studied,　which　provided　a　base　for　adjusting　the　structure　of　public　traffic　by　using　the　fare　policy.　Subways　and　buses　are　the　primary　compositions　of　the　city　public　transit　system;　however,　in　big　cities,　the　passenger　flow　split　is　always　unreasonable　between　subways　and　routine　buses.　According　to　the　questionnaire　investigations　of　subways　and　buses　routes　split　in　Beijing,　a　split　modal　is　given　in　this　paper.　It　provided　a　tool　for　using　traffic　policy　to　adjusting　the　structure　of　public　transit　system.　©　2010　ASCE.