Traffic　simulation　is　an　effective　means　for　the　optimal　design　of　an　intersection.　However,　the　foreign　simulation　software　can＇t　be　directly　applied　in　China　because　of　the　influence　of　the　mixed　traffic.　So　it　is　necessary　to　develop　the　simulation　system　based　on　China＇s　traffic　characteristics.　This　paper　presented　the　methods　of　the　design　and　realization　of　the　simulation　optimization　system,　with　an　isolated　signalized　intersection　as　an　example.　Through　the　expert＇s　investigation,　the　paper　summarizes　the　existent　problems　and　parameters　and　the　expert＇s　schemes　of　the　signalized　intersection.　Then　the　knowledge　base　and　the　inference　engine　of　the　expert＇s　system　are　designed.　Based　on　the　design,　the　paper　realizes　this　system　by　writing　VB　code.　It　can　export　the　optimized　schemes　automatically　by　inputting　the　intersection　parameters.　In　addition,　the　system　is　also　an　open　system　which　permits　the　users　to　add　in　the　rule　bases　and　the　scheme　collections　according　to　the　user＇s　different　demands　and　the　changes　of　the　intersection　conditions.　The　research　indicates　that　the　system　is　applicable　for　the　signalized　intersection.　©　2010　ASCE.