There　is　much　research　on　car-following　criterion　such　as　headway　and　headway　distance.　But　most　of　these　works　focus　on　Highway　or　Motorway　segments　excluding　intersections.　This　paper　studies　the　car-following　criterion　in　a　signalized　intersection.　The　close-range　photogrammetry　system　is　built　to　collect　and　analyze　traffic　data　in　a　signalized　intersection　of　Beijing.　The　speed　difference　analysis　method　is　performed　to　distinguish　the　car-following　status　by　getting　the　critical　headway　and　headway　distance.　The　results　show　that　the　critical　headway　of　the　car-following　in　a　signalized　intersection　is　3s　and　the　critical　headway　distance　is　30m.　The　main　contributions　of　the　paper　are　that　a　close-range　photogrammetry　system　available　to　traffic　observation　is　built　and　speed　difference　analysis　is　especially　available　to　judge　the　car　following　status　in　signalized　intersection.　©　ASCE.