In　this　paper,　based　on　the　analyzing　(he　signal　control　problem　of　single　intersections,　a　kind　of　real-time　optimization　method　with　PSO　(Particle　Swarm　Optimization)　solving　signal　timings　for　single　intersection　is　put　forward.　On　detecting　the　flow　of　current　cycle　and　the　cycle　before,　estimating　the　flow　of　next　circle　is　proceeded.　Setting　least　delay　as　performance　index,　we　get　each　phase　time　for　the　next　cycle.　A　simulation　experiment　for　the　traffic　model　at　a　four-phase　intersection　is　also　performed.　The　result　shows　that　the　method　is　efficient.