Based　on　the　field　data　collected　from　Beijing,　Shanghai　and　Guangzhou　city,　this　study　applied　regression　analysis　method　to　build　speed-flow　relationship　model　and　furthermore　calibrated　Greenshields　model.　Considering　results　of　two　aspects　synthetically,　the　ideal　capacity　of　expressway　and　correctional　coefficients　of　different　lanes　are　recommended.　Consequently　this　study　can　not　only　provide　reference　for　the　planning,　design　and　operation　analysis　of　expressway,　but　also　help　to　revise　the　interrelated　code　or　criterion　of　urban　streets.