The　traffic　volume　forecasting　models　on　the　outmost　lane　of　merging　influence　area,　diverging　influence　area　and　weaving　area　of　the　urban　expressway　cloverleaf　interchange　and　the　time　headway　distribution　models　at　the　same　section　were　built.　Based　on　test　data,　capacity　models　of　three　influence　areas　of　cloverleaf　interchange　of　expressway　in　above　were　calibrated.　The　capacity　forecasting　model　of　the　whole　cloverleaf　interchange　was　built　based　on　research　outcome　in　above　which　was　used　to　calculate　the　capacity　of　cloverleaf　interchange,　and　the　model　was　validated　by　the　simulation　method.　Results　show　that　the　proposed　model　is　the　theoretic　base　of　studying　interchange　capacity　on　urban　expressway.